Merge pull request #5 from r3/master

More working, less repeats
MAJOR UPDATE, Now with more everything!

Updated and extended: metadata
Added: Skip, User Login, Verify
Renamed and extended: display_mix (request_mix), mix_selection (ask_which)

Known Bugs:
report_performance
- If mpg123 errors out, mostly due to mp4 or m4a files, is doesn't get called until the NEXT PLAYABLE TRACK. This results in the currently playing song being reported more than once.
Create user_context.py

This houses all the user context stuff, (un)liking mixes/tracks, (un)following users, etc.
Create user_test.py

testing functions.