- UTF-16 Unicode Text (TXT) write
- Lotus Formatted Text (PRN) read/write
- DBF version 2 field length adjustments
- throw errors if SheetNames is invalid (fixes#376 h/t @pietersv)
- chartsheets are now stored as sheets with "!type" set to "chart"
- fixed Strict XML Workbook Relationships
- stubbed support for dialog and macro sheets
- removed legacy XLS `!range` field