Cleanup/modernize code

[pfalcon]

The project has some dead code. That's definitely true with my refactorings, but probably was true even with code as was in CPython2.

Also, non-canonical use of constructors, etc. is there, brush it up/rewrite.

While doing this still consider compatibility with Python2.7 for extra points.

[pfalcon]

Ok, in pfalcon/python-compiler@51a840a, older no longer used AST-related modules are removed.

[pfalcon]

Good progress on removing dead code today.