Create UserPrefs

Create User Preferences model.
Regiser UserPref with admin.
UserPrefs: add ArtistsStarred and ConcertsStarred.

Conflicts:
	boricide/models.py
Ignore datafixtures.
Event model will set advance_price = door_price, when advance_price not set.
When lat and lng cant be retrieved from database, dont save 'Event' model.
use pygeocoder to convert geocode venue address.
Cleanup
Venue model: Allow user to provide coords, and geocode if coords not provided.