Formatting according to PEP8.
De-camelcase assigned names
Limit to ImportException and note fallback
Move default_itag_order out of YTURL class
Move strip_to_video_id outside of YTURL class.
Move itag_order outside YTURL class.
Move available_itags outside YTURL class.
Beautify available_itags.
Move parse_quality_group outside YTURL
Remove YTURL block, move remaining code to __main__ block
Remove semi-useless "live" tests
Clean up docstrings for rST
Tersify messages a little.
Separate functions and the __main__ block by two blank lines.
Tersify README.
Merge branch 'refactor'