Start work on documentation

This test adds the basic documentation stuff including testing. I've
started the documentation itself by copying the README, as it served as
documentation so far.

The goal going forward will be to shape it up into something more
documentation-y.
Add API documentation
Remove compatiblity and links section from docs

These make more sense to have in the README
Add License to documentation
Add duplication comment to setup.py

This probably should be made unncessary by programmatically determining
the version.
Use Sphinx roles where applicable
Add Generating Lexers document
Fix wording
Add document on generating parsers
Remove parts of index document covered elsewhere
Use correct token name
Add section on error handling
Add a section about state
Merge pull request #21 from DasIch/docs

Adding Documentation