Initial commit of Version 3.0.0.

This new version contains:

1. The ability to create Excel 2007 (XLSX) files in addition to Excel 2003 (XLS) files.

2. The Perl package Excel::Writer::XLSX is now included to facilitate the creation of the Excel 2007 files.

3. The Perl package Text::CSV_XS has been replaced with Text::CSV_PP, which is a Pure Perl implementation of the former package and is included in the WriteXLS package. This should make it easier for users to install WriteXLS since a pre-compiled or locally compiled binary for Text::CSV_XS is no longer required.

4. Data frame columns that have a 'comment' attribute, created using the comment() function, will have the text content of the 'comment' attribute written to a cell comment in the first row of the worksheet containing that data frame. This will work for both Excel 2003 (XLS) and Excel 2007 (XLSX) files. These comments can serve as column labels, providing descriptive information on the content of the column in the Excel worksheet.