Enable install of CLI script.

These revisions enable **python setup.py install** to place a CLI of
**guessit** to the system's default Python CLI directory (e.g.
**/usr/local/share/python/** on OSX with Python installed via Homebrew).
As a result, a user can simply issue the command **guessit** instead of
the current **python guessit.py**.
Merge pull request #25 from dplarson/master

Revise setup.py to enable install of guessit CLI