Basic support for Generators
Currently does not support arguments and only a single generator at a time is allowed

In addition added 'StopIteration' iteration support
Add support for generator arguments
kwargs are unsupported for now
Generators: remove single instance restriction and handle generators inside closures
Merge branch 'master' of https://github.com/dropbox/pyston into generators

Conflicts:
	src/codegen/irgen/irgenerator.cpp
	src/codegen/runtime_hooks.h
Merge branch 'master' of https://github.com/dropbox/pyston into generators

Conflicts:
	src/codegen/runtime_hooks.h
	src/runtime/builtin_modules/builtins.cpp
Merge branch 'master' of https://github.com/dropbox/pyston into generators

Conflicts:
	src/codegen/compvars.h
	src/codegen/runtime_hooks.h
	src/runtime/objmodel.h
Generator: implement basic review comments
Generator: fix *args and **kwargs handling
Merge pull request #108 from undingen/generators

Implement Python Generators