Work on generator frontend
Generation object, typing and fusion
Fix-point generator fusion pass
Properly update type context in dataflow pass
Hack in some phases
Improve phase management and tracking
Don't rewrite generator object return, still rewrite calls in generators
Fix-point generation fusion pass across dependences, flatten loop nesting forest
enumerate/zip, generator tests (TODO: try/except for zip())
Merge branch 'master' of github.com:ContinuumIO/numba-lang