Test create a File and add a Sheet to the file.
Add AddRow method to Sheet.
Add docstring to test.
Split out lib.go and lib_test.go to several smaller files, this helps make things a bit more readable.
Working implementation of numericToLetters.
Add alpha cell ID to cell in output.
Test passing on first version of sheet marshalling.
Add some docstrings.
Test we can create a RefTable, populate it, use it to deference shared string
IDs and derive an xlsxSST from it.
Make NewXlsxSSTFromRefTable into RefTable.makeXlsxSST, for consistency.
Turn shared string RefTable into a struct instead of straight slice.
Marshal xlsxSST and xlsxWorksheet.
Create xlsxStyles from a sheet's Styles.
Check in current state of writeable-xlsx so I can switch branches
Allow setting of fill patterns on cell.
Marshal multiple sheets.
Commit current state for safety
Build workbook.xml.rels file, and use sheetnames instead of positional indexes
in File.Sheets
Put sharedStrings.xml in workbook.xml.rels
Write out the static .rels and app.xml