pivottabler 1.5.4
=================

This release includes one improvement and one change in anticipation of R 4.3.0.

Improvements
----------------

`pt$findCells()` gains additional arguments `lowN` and `highN`.  These arguments allow the cell with the min/max value or the N cells with the lowest/highest values to be easily found.  

When either of these arguments is specified, the list of cells returned from `pt$findCells()` is sorted into the corresponding order by cell value.

Examples:

- Specifying `lowN=1` will find the cell with the lowest value.
- Specifying `highN=1` will find the cell with the highest value.
- Specifying `lowN=5` will find the five cells containing the lowest values, sorted into ascending order by cell value.
- Specifying `highN=5` will find the five cells containing the highest values, sorted into descending order by cell value.

R 4.3.0 Change
----------------

The change described below will not affect most pivottabler package users.

R 4.3.0 includes a fix/breaking change that affects how the base R match() function works and how the %in% operator works.  Specifically Date, POSIXct and POSIXlt values are matched as character values from R 4.3.0 rather than their underlying internal value.  This breaks one of the pivottabler package automated tests.  Whilst fixing this test, the opportunity was also taken to to improve how pivottabler filters work with Date, POSIXct and POSIXlt values when filters specify more than one value of these types (e.g. when visual totals are in use) by replacing uses of the `base::intersect()`, `base::union()` and `base::unlist()` functions with versions that better handle Date, POSIXct and POSIXlt values.


pivottabler 1.5.3
=================

Improvements
----------------

Tables can now be exported to a wider variety of file formats using the basictabler and flextable packages.  In addition to HTML, Latex and Excel (which can be generated directly by the pivottabler package), additional formats now supported using basictabler+flextable include include Microsoft Word, Microsoft PowerPoint and PDF.  See the Outputs vignette for more details. 

It is now easier to format the borders for specific cells.  See the "Formatting cell borders for specific cells" section of the Styling vignette for more details.


pivottabler 1.5.2
=================

Bug Fixes
----------------

This release includes one small bug fix that sometimes affected pivot tables that were converted to basic tables (from the `basictabler` package) and which then were exported to an Excel file.  The issue caused row/column headings for totals or calculations (when multiple calculations are defined) to appear blank when the `basictabler` table was exported to Excel.  This issue has been resolved in two ways:  
1) Headings (such as totals and calculation names) now have a raw value specified in the converted `basictabler` table.
2) The `basictabler` package now (by default) will write the formatted value to the Excel file if no raw value exists.


pivottabler 1.5.1
=================

Breaking Changes
----------------

**stringsAsFactors in R 4.0.x and 4.1.x**

From R 4.1.0, the default value of the `stringsAsFactors` argument in `tbl$asDataFrame()` changes to FALSE due to the deprecation of `default.stringsAsFactors()`.  When the package is used on versions of R < 4.1.0, the package behaviour is unchanged.  When the package used on R 4.0.x versions, a warning message is displayed about the change in future behaviour.  The logic for this change was actually implemented in version 1.5.0 of the package but the impact will be felt with the release of R 4.1.0.

Bug Fixes
---------

* Resolved error "getSimpleColoredTheme(): colors must be specified." that was sometimes encountered when using a simple theme as a list that is assigned to the pivot table `pt$theme` field.


pivottabler 1.5.0
=================

Overview
--------

This release includes one potentially breaking change and many small enhancements across various parts of the package.

Reminder:  The package now only contains one introductory vignette (due to the constraints on CRAN).
The full set of 15+ vignettes can be found at:  http://www.pivottabler.org.uk/articles/ 

Breaking Changes
----------------

**Stricter definition of empty cells**

When retrieving cells using `pt$getCells()` with the `excludeEmptyCells` parameter, or when  searching cells using `pt$findCells()` with the `emptyCells` parameter, previous versions of the package would only treat cells as empty if they were related to a data group marked as empty.  Cells with NULL values were not considered as empty.

Starting with this version, cells with NULL values (i.e. where `is.null(cell$rawValue)==TRUE`) are also regarded as empty.  This may result in more cells being regarded as empty.  The previous behaviour is still available by specifying `compatibility=list(legacyEmptyCellMatching=TRUE)` as an argument when creating the pivot table, either in `PivotTable$new()` or one of the quick pivot functions such as `qpvt()`.

Improvements
----------------

* `pt$findRowDataGroups()` and `pt$findColumnDataGroups()` gain new arguments `rowNumbers`, `columnNumbers` and `cells` to restrict the data group search based on combinations of row/column numbers and/or cells.  See the "Finding and Formatting" vignette for details.
* New property `pt$allCells` provides a simple way to retrieve a list of all cells in the pivot table.
* `pt$getCells()` gains new arguments `groups`, `rowGroups` and `columnGroups` making it easier to retrieve cells related to specific data groups.  See the "Finding and Formatting" vignette for details.
* `pt$getCells()` also gains a new `matchMode` argument making it easier to retrieve cells based on combinations of row and column criteria.  See the "Finding and Formatting" vignette for details.
* `pt$findCells()` gain new arguments `rowNumbers`, `columnNumbers`, `cellCoordinates`, `groups`, `rowGroups`, `columnGroups`, `cells` and `rowColumnMatchMode` to restrict the cell search based on combinations of row, column and cell criteria.  See the "Finding and Formatting" vignette for details.
* `pt$findCells()` also gains new argument `valueRanges` to enable more granular logic to be specified when matching cell values.  See the "Finding and Formatting" vignette for details.
* `pt$setStyling()` gains new integer/numeric vector arguments `rowNumbers` and/or `columnNumbers`.  It is now also possible to specify only a set of row numbers and then all cells in those rows will be styled (and similarly for column numbers).  Previously, if only row numbers or only column numbers were specified, then no cells would be styled.  Users who require the old logic can specify the argument `compatibility=list(legacySetStylingRowColumnNumbers=TRUE)` when calling `PivotTable$new()`.
* New method `pt$mapStyling()` simplifies applying styling to cells based on cell value, e.g. banding by value into different colours or colour gradients.  See the "Styling" vignette for details plus the "Finding and Formatting" vignette for a couple more examples.
* When using a simple theme (specified as a list) to style a pivot table, it is now possible to specify a font size.  Thanks to @msgoussi for the suggestion (#48).  See the "Styling" vignette for details.
* The following now accept vector/list arguments: `pt$getColumnGroupsByLevel()`, `pt$getRowGroupsByLevel()`, `pt$getLeafColumnGroup()`, `pt$getLeafRowGroup()`, `pt$findGroupColumnNumbers()` and `pt$findGroupRowNumbers()`.
* Several new outline parameters are now supported to simplify styling when generating row data groups from a variable depth hierarchy.  See "Variable Depth Hierarchy Example" in the "Regular Layout" vignette for details. 

Bug Fixes
---------

* Cell styles are now inherited correctly from calculations and data groups (#46).  Thanks to @msgoussi for the bug report.  An explanation of the style inheritance rules has also been added to the "Styling" vignette.


pivottabler 1.4.0
=================

Overview
--------

This release includes one potentially breaking change and many small enhancements across various parts of the package.

Reminder:  The package now only contains one introductory vignette (due to the constraints on CRAN).
The full set of 15+ vignettes can be found at:  http://www.pivottabler.org.uk/articles/ 

Breaking Changes
----------------

**Row group and column group captions for blank values**

When generating HTML, previous versions of the package would not output any caption for data groups with a blank null (e.g. NULL).  This could lead to rows collapsing to a few pixels in height (if all of the cells on the row also had no value).  Starting with v1.4.0, a non-breaking space character is emitted instead (HTML &amp;nbsp;), in the same way that other parts of the pivot table sometimes also emit a non-breaking space character.   This should make minimal difference to the visual appearance of the table, however it may cause issues for users who require the previous behaviour.  The previous behaviour is still available by specifying `compatibility=list(noDataGroupNBSP=TRUE)` as an argument when creating the pivot table, either in `PivotTable$new()` or one of the quick pivot functions such as `qpvt()`.

A future version of the package will likely include an option to prevent all non-breaking space characters from being emitted and more correctly use CSS style rules instead to control minimum data group heights/widths. 

Documentation Changes
---------------------

* The code documentation for `pivottabler` has been re-written to use the new R6 documentation capabilities in `roxygen2`.  As a result the documentation is now more detailed than in previous versions, e.g. arguments in object method calls are now properly documented.  Nonetheless, the easiest way to learn the package is using the vignettes.  
* The new "Navigating a Pivot Table" vignette provides more detailed information about low-level methods for navigating in code over the different parts of a pivot table.  Several new methods have also been added that are described in this vignette:  `pt$getLeafColumnGroup()`, `pt$getLeafRowGroup()`, `pt$getCell()`, `pt$getColumnGroupsByLevel()`, `pt$getRowGroupsByLevel()`, `pt$columnGroupLevelCount` and `pt$rowGroupLevelCount`.
* The "Irregular Layout" vignette has been expanded to provide additional information to help with building custom pivot tables.

Improvements
----------------

* Defaults can now be set using `pt$setDefault()` for the following parameters of `pt$addColumnDataGroups()` and `pt$addRowDataGroups()`: `addTotal`, `expandExistingTotals`, `visualTotals`, `totalPosition`, `totalCaption`, `outlineBefore`, `outlineAfter` and `outlineTotal`.  
* The captions of data groups added to pivot tables using `pt$addColumnDataGroups()` and `pt$addRowDataGroups()`can now be specified using the new `caption` argument.  See the "Data Groups" vignette for details.
* Custom sort orders can be specified for data groups.  See the "Data Groups" vignette for details.
* Empty rows/columns can be found using the new functions `pt$getEmptyRows()` and `pt$getEmptyColumns()`.  See the "Custom Layout Changes" section of the "Irregular Layout" vignette for details. 
* The `pt$findRowDataGroups()` and `pt$findColumnDataGroups()` functions gain additional parameters: `atLevels`, `minChildCount`, `maxChildCount` and `outlineLinkedGroupExists`.  See the "Finding and Formatting" vignette for details.
* When deleting data groups using `group$removeGroup()`, it is now possible to also remove the related groups such as the outline group header row (aka. outline before) and outline group footer row (aka. outline after) using the new argument `removedRelatedOutlineGroups=TRUE`.
* Specific rows and/or columns can be removed from pivot tables using new functions such as `pt$removeRow(3)` and `pt$removeRows(c(2, 4))`.  See the "Custom Layout Changes" section of the "Irregular Layout" vignette for details. 
* `pt$addRowDataGroups()` gains two new arguments `onlyAddGroupIf` and `onlyAddOutlineChildGroupIf` which enable hierarchies with a variable number of levels to be used on rows in a pivot table in outline layout.  See the "Regular Layout" vignette for details.  Thanks to @MarcoPortmann for the usage scenario.
* When exporting to a data frame, it is now possible to also export the row groups as columns (instead of only row names) using `pt$asDataFrame(rowGroupsAsColumns=TRUE)`.  Thanks to @ismailmuller for the suggestion (#29).
* When exporting to a data frame, the handling of cell values that are not integer/numeric can be specified using the `forceNumeric` argument. `TRUE` will convert any values that are not integer/numeric to NA.
* Row group headers, visible when specifying `pt$renderPivot(showRowGroupHeaders=TRUE)`, are now set automatically to the variable name when calling `pt$addRowDataGroups(...)`.  The name can be overridden using `pt$addRowDataGroups(..., header="...")`.
* Additional arguments can now be passed to custom calculation functions using the `calcFuncArgs` argument.  See the "Calculations" vignette for details.  Thanks to @MarcoPortmann for the suggestion (#31 and #32).
* It is now possible to pre-calculate totals/aggregate data cells when using calculation method 4 ("Showing a value").  See the "Calculations" vignette for details.  This closes a long-standing gap with this calculation method. (#2).

Deprecated
----------------

The following can still be used but now emits a deprecation warning:

* The `getLevelNumber()` method on data groups has been replaced with the `levelNumber` property.


pivottabler 1.3.1
=================

This release includes two small bug fixes only:

* Pivot tables with nothing on the rows axis fail to convert to a data frame using `pt$asDataFrame()` (issue #30).
* Pivot tables with nothing on rows and/or columns sometimes fail to convert to a matrix using `pt$asMatrix()` or `pt$asDataMatrix()`.


pivottabler 1.3.0
================

Overview
--------

This release introduces a new layout type - outline layout - that can make larger pivot tables with multiple levels of row groups more readable and more visually appealing.  

Several small improvements mean that irregular pivot tables (e.g. two pivot tables in one) are now easier to construct.

The package vignettes have grown too large be hosted on CRAN.  They have been moved to:  http://www.pivottabler.org.uk/articles/ 

Improvements
----------------

* A new "outlined" layout is now supported (in "beta" in this release).  This generates additional rows for row data groups which appear as headings within the pivot table.  See the new "Regular Layout" vignette for details.
* Several small improvements make building irregular layouts much easier, including: 
   * adding empty rows and columns, e.g. using `pt$addRowGroup(caption="By Size", isEmpty=TRUE)` or `pt$addColumnGroup(...)`,
   * adding individual data groups, e.g. using `pt$addRowGroup(variableName="Size", values="Small")` or `pt$addColumnGroup(...)`,
   * adding total data groups, e.g. using `pt$addRowGroup(variableName="Size", isTotal=TRUE)` or `pt$addColumnGroup(...)`.
   * Several other options that are described in the "Irregular Layout" vignette.
* Headings for the row data groups (i.e. headings for the first column / first few columns) in a pivot table can now be specified.  See the "Pivot tables as standard tables (row group headings)" section in the "Data Groups" vignette for details.  The new `showRowGroupHeaders` argument can be used with `pt$renderPivot()`, `pt$getHtml()`, `pt$saveHtml()`, `pt$writeToExcelWorksheet()` and `pt$asBasicTable()`.
* New function `pt$asDataMatrix()` provides a cleaner way to convert a pivot table to a matrix, where the row/column headings in the pivot table become the row/column headings in the matrix.  See the "Outputs" vignette for details.
* New function `setStyling()` provides an alternative method to set style declarations on data group headers and cells.  See the "Finding and Formatting" or "Irregular Layout" vignettes for examples.
* Additional arguments can now be passed to custom functions used to format calculation values.  See the `fmtFuncArgs` parameter in the "Calculations" vignette for details.
* Additional arguments can now be passed to custom functions used to format data group values.  See the `fmtFuncArgs` parameter in the "Data Groups" vignette for details.

Bug Fixes
----------------

The `atLevel` argument of `pt$addColumnDataGroups()` and `pt$addRowDataGroups()` now behaves correctly / more intuitively.  Previously it would often add the data groups at the level below the level expected.

Deprecated
----------------

The following can still be used but now emit a deprecation warning:

* `pt$getTopColumnGroups()` has been deprecated and replaced with `pt$topColumnGroups`.
* `pt$getLeafColumnGroups()` has been deprecated and replaced with `pt$leafColumnGroups`.
* `pt$getTopRowGroups()` has been deprecated and replaced with `pt$topRowGroups`.
* `pt$getLeafRowGroups()` has been deprecated and replaced with `pt$leafRowGroups`.


pivottabler 1.2.3
=================

This release includes one small bug fix only:
Adding more than nine calculations causes the calculation columns to appear in the wrong order (issue #25).


pivottabler 1.2.2
=================

This release includes one small bug fix only:
Calling pt$setStyling(cells=...) on an empty list of cells now succeeds without an error (issue #23).


pivottabler 1.2.1
=================

This release includes one small bug fix only:
Calling pt$asDataFrame() on a pivot table containing blank/NA cells now succeeds without an error (issue #20).


pivottabler 1.2.0
================

Overview
--------

This release includes one small potentially breaking change and one bug fix.

Breaking Changes
----------------

**Changes to rowspan and colspan attributes in HTML**

When generating HTML, previous versions of the package would always generate rowspan and colspan attributes for merged table cells, even if the number of rows or columns being spanned was only one.  Starting with v1.2.0, rowspan and colspan attributes are only generated where the number of rows or columns being spanned is greater than one.  This should make no difference to the visual appearance of the table, however it may cause issues for users who require the previous behaviour.  The previous behaviour is still available by specifying `compatibility=list(explicitHeaderSpansOfOne=TRUE)` as an argument when creating the pivot table, either in `PivotTable$new()` or one of the quick pivot functions such as `qpvt()`.

Improvements
----------------

Small improvements have been made to the conversion of pivot tables to basic tables (in the `basictabler` package).  Starting from this version of `pivottabler` and v0.3.0 of `basictabler` the HTML that is generated from the two packages should be more consistent.  Previously, `basictabler` would render row/column header cells using the HTML **td** element instead of the more correct **th** element.  Thanks to @rickwargo for reporting this difference in HTML output between the two packages.

Bug Fixes
----------------

Calling `pt$setStyling()` on the same cell multiple times now succeeds (previously failed with error).


pivottabler 1.1.0
================

Overview
--------

This release includes:

* Ability to convert a pivot table to a basic table (from the basictabler package)
* Many small styling improvements
* More styling information and examples in the vignettes

Breaking Changes
----------------

This version of `pivottabler` generates slightly different CSS/HTML for the built-in themes/styling compared to previous versions.  The visual appearance is unchanged.  This may be a breaking change for users who require the generated CSS/HTML code to be identical to previous versions.

More details:

In version 1.0.0 and earlier versions of `pivottabler`, the built-in themes used a shared set of style declarations for both calculation value cells and total cells.  From `pivottabler` version 1.1.0 onwards, total cells use a separate set of style declarations.  The visual appearance of pivot tables using the built-in themes has not changed, only the HTML/CSS that is generated is slightly different - so the great majority of users will not be affected.  

This change reduces the risk of styling changes to totals accidentally affecting all calculation value cells and vice-versa.  

The output of earlier versions, where total cells and calculation value cells use a shared set of style declarations, can be generated by specifying `compatibility=list(totalStyleIsCellStyle=TRUE)` as an argument when creating the pivot table, either in `PivotTable$new()` or one of the quick pivot functions such as `qpvt()`.

Improvements
----------------

* Convert a pivot table to a `basictabler` table - enabling flexible/arbitrary changes to be made to pivot tables after they have been created, e.g. inserting or deleting rows/columns/cells.  See the "Outputs" vignette for more details.
* New function `pt$setStyling()` simplifies the setting of formatting and styling on data groups and table cells.  See the "Styling" vignette for details.
* Specifying styling/formatting when creating pivot tables using the `qpvt()` and `qhpvt()` functions is now possible.  See the "Introduction" vignette for a list of parameters for these functions.  See the "Styling" vignette for more examples.
* Specifying styling/formatting when creating pivot tables using the verbose syntax is also now possible - styling can be specified when adding data groups and when adding calculations to pivot tables.  Again, see the "Styling" vignette for more details and examples.
* A more detailed explanation of styling rules has been added to the "Styling" vignette.


pivottabler 1.0.0
================

Breaking Changes
----------------

* The default value of the `specifyCellsAsList` argument in the `pt$getCells()` function has been changed to `TRUE`.
The previous usage of the `pt$getCells()` function is still supported (now you must explicitly specify `specifyCellsAsList=FALSE`).  This change has been planned since v0.3.0 (June 2017) and a warning message has been displayed since then.  See the Finding and Formatting vignette for more details on the `specifyCellsAsList` argument. 
* Additional checks are now made to prevent calculations being moved/added after the calculation row/column groups have been generated.   There is a small chance this will cause errors in existing user code - though this will only occur where user code is trying to move/add calculations after the calculations have already been set in the pivot table by a call to `pt$addColumnCalculationGroups()` or `pt$addRowCalculationGroups()` (previously this would silently fail).

Improvements
----------------

* pivottabler now supports using any of the following data types in both row/column headings and cell values: integer, numeric, character, logical, Date, and POSIXct.
* Improved support for illegal data frame column names and illegal calculation names (e.g. including spaces or symbols such as dash, plus, dollar, etc).  See  the Details Appendix (A1) vignette for details.
* The new `PivotFiltersOverrides` class provides many new options for overriding the data used to calculate cell values.  It is now possible to add to, remove from or entirely replace filter criteria as part of calculation definitions.  This makes calculations such as "% of row/column/grand total", ratios/multiples, rolling averages and cumulative sums easier.  See the Calculations Appendix (A2) vignette for examples.
* Row/column heading style settings for data groups can now be declared up-front using the `baseStyleName` and `styleDeclarations` arguments in `pt$addColumnDataGroups(...)` and `pt$addRowDataGroups(...)`.  See the Styling vignette for an example.
* Row/column heading style settings for calculations can now be declared up-front using the `headingBaseStyleName` and `headingStyleDeclarations` arguments in `pt$defineCalculation(...)`.  See the Styling vignette for an example.
* Cell style settings for calculations can now be declared up-front using the `cellBaseStyleName` and `cellStyleDeclarations` arguments in `pt$defineCalculation(...)`.  See the Styling vignette for an example.
* Additional `exportOptions` parameter when exporting to HTML, Latex and Excel for controlling how NA, NaN, -Inf and Inf are exported.  See the Details Appendix (A1) for more information.
* Additional parameter `outputHeadingsAs` in `pt$writeToExcelWorksheet(...)` to control how row/column headings are formatted when exporting to Excel.  See the Excel Export vignette for more details.
* `pt$asDataFrame(...)` and `pt$asTidyDataFrame(...)` now support additional parameter `stringsAsFactors` with default value `default.stringsAsFactors()`.

Bug Fixes
----------------

* Bug fixed that would cause corrupt Excel files to be generated when exporting pivot tables with no row/column groups to Excel.

Upcoming Changes
----------------

No breaking changes currently planned.

pivottabler 0.4.0
================

Breaking Changes
----------------

* Removed support for R 3.2.x.  Minimum supported version of base R now R 3.3.0. 

Improvements
----------------

* It is now possible to output a pivot table to an Excel file with one line of R, including with styling that closely matches the HTML output.  See the Excel Export vignette for more details. 
* Quick-pivot functions now support showing/hiding totals and renaming the captions of totals, which was previously only possible using the verbose syntax.  See the Introduction vignette for more details.

Bug Fixes
----------------

* Corrections to ordering of code in Styling vignette.
* A couple of other small bug fixes.

Upcoming Changes
----------------

* The previous usage of the arguments for the getCells() function is still supported (and is still the default) however the new argument usage will be made the default in a future version.  For now, a message is displayed noting the upcoming change.  See the Finding and Formatting vignette for more details.

pivottabler 0.3.0:  Performance Improvements and Quick-Pivot Functions
================

Breaking Changes
----------------

* Pivot table initialiser parameters renamed from messages and messageFile to traceEnabled and traceFile respectively. 

Improvements
----------------

* pivottabler now calculates cell values in batches in order to reduce the calculation time required for larger data frames.  For large pivot tables based on large data frames this typically results in a big performance improvement, e.g. for a pivot table of 1000 cells based on a data frame with 10 million rows the rendering time is around 7 seconds in version 0.3.0 compared to over 480 seconds in version 0.2.0.  See the new Performance vignette for more details.
* pivottabler now also supports the data.table package for performing pivot table summary/aggregation calculations.  dplyr remains the default however data.table offers a moderate performance improvement for large data frames (10 million rows and above).  See the Calculations vignette for more details.
* addRowDataGroups and addColumnDataGroups functions pre-group the data to reduce the time required for larger data frames.
* New argumentCheckMode parameter added to pivot table initialiser to provide an additional option to reduce the time required to create larger pivot tables.
* print() method added to PivotTable class.  Can now print a simple plain text view of the pivot table to the console using just `pt` or retrieve the plain text as a character value using `pt$asCharacter`.
* Quick-pivot functions added that construct a basic pivot table with one line of R: `qpvt()`, `qhpvt()` and `qlpvt()`.  See the Introduction vignette for more details.
* Internal pivot filters class differentiates more clearly between 'all', 'some' and 'none' match cases for more robust filtering and early elimination of some cell calculations.
* The getCells() function has been made more intuitive to use when getting specific cells by using a new cellCoordinates argument.  See the Finding and Formatting vignette for details.
* Stricter name checking for calculation names to avoid later unclear dplyr/data.table errors caused by syntax errors arising from illegal names.

Bug Fixes
----------------

* Various small bug fixes.

Upcoming Changes
----------------

* The previous usage of the arguments for the getCells() function is still supported (and is still the default) however the new argument usage will be made the default in a future version.  For now, a message is displayed noting the upcoming change.  See the Finding and Formatting vignette for more details.

pivottabler 0.2.0:  New Output/Conversion Options, New Find Options
================

Breaking Changes
----------------

(none)

Improvements
----------------

* Added the ability to output a pivot table in Latex.
* Added the asMatrix() function to allow the pivot table contents to be retrieved as a matrix.
* Added the asDataFrame() and asTidyDataFrame() functions to allow the pivot table contents to be retrieved as a data frame.
* Added findRowDataGroups() and findColumnDataGroups() functions to find data groups (i.e. headings) that match specified criteria to simplify scenarios such as changing the styling of specific headings.
* Added the getCells() function to retrieve cells by row number and/or column number.
* Added the findCells() function to find cells in the body of a pivot table that match specified criteria to simplify scenarios such as conditional formatting.
* Five new vignettes added.  Many changes to the existing vignettes.
* Modified the sample data by specifying a time zone (UTC) for all POSIXct data to remove inconsistencies when using the data in different time zones. 
* Modified the automated tests to no longer use the digest package.
* Updated object documentation to wrap lines longer than 80 characters.

Bug Fixes
----------------

* Various small bug fixes.
* Shiny vignette examples now working.

pivottabler 0.1.0
================

Initial version.
