Add support for the ragel state-machine generator.

Testing Done:
Ran the new unit tests.

Also converted wikid in birdcage to use this, and tested it.  That's on birdcage in dturner-ragel-oss-pants.

Bugs closed: https://github.com/pantsbuild/pants/issues/353

Reviewed at https://rbcommons.com/s/twitter/r/678/