Refactor

[vmuriart]

Refactor of grouping.py to simplify/clarify the different sections.

note, small behavior change on invalid identifiers introduced. Otherwise behavior should be the same

[coveralls]

Coverage decreased (-0.7%) to 88.299% when pulling 1e770d9 on vmuriart:refactor into 9ab1464 on andialbrecht:master.

[vmuriart]

I'm porting back various refactored sections from my fork. I'll submit various small pr instead of a massive one with all the changes.

coverage decrease most likely due to some of the utilities already backported but not being used yet.

[andialbrecht]

Wow! Thanks a lot! The code looks more modern and since all tests pass I think it's fine to merge it. I just skimmed through the changes as the changeset is pretty large. But it looks good so far!

[vmuriart]

@andialbrecht I'm being really careful on which sections of code after being ported at which point from my fork to avoid introducing any breaking behaviors.

The lexer was the next one I was thinking about porting back. Wasn't sure if there was any particular reason you went with using a meta class instead of regular functions or a regular class.