Updated grammar to allow for some punctuation in the strings :P
Cleanup
Added NoSuchGrammar exception in appropriate places, and added 'enforce_types' for annotation type checking
Added hopeful milestone
Use absolute path for programs
Defining functions now works :D
Cleanup, reorganisation, and some documentation

Cleanup
Reorganisation
Some documentation
Renamed Tyrian.run to Tyrian.compile
Added some comments, and added convenience function for returning values
Cleanup
Rewrote ParseTree.pprint