Tribix 2.3.1 released

I'm pleased to announce that Tribix 2.3.1 is released.

Some main changes follow:

1. Support BIRT 2.2/2.3 series.
2. Add hyperlink support for PPT and RTF.
3. Add comments support for XLS
4. Make source code compatible with BIRT 2.2.
5. Update POI dependency to 3.2 Final.