Fixed appendix label in TOC. Fixed spacing in TOC.
Only number (letter) appendices if there are more than one.

Note that this requires three passes to work correctly for multiple
appendices. The headings are fixed on the second pass. The TOC entries
are fixed on the third pass.
Merge pull request #30 from godbyk/master

Provides appendix support

Kevin is a wizard. This will automatically, and only, number appendices if there are more than one.