Add code for a range function that uses generators.
Add code for a range function that uses generators.

Cleaned up existing code by abstracting code to parse arguments.  Also removed
any unneeded operations (such as calling 'int' on a division when using floor
division also works).  Fixed a bug where the values  returned by
OldStyleRange could be short by one value.  Added more documentation.

Testing code also has a basic sanity check.

sk-/python2.7-type-annotator,sk-/python2.7-type-annotator,sk-/python2.7-type-annotator