Added a function to get all unjoined groups of a user
Added a function to get all unjoined groups of a user
The helper function can expect a user instead of expecting a username.
Merge branch 'master' into Get_UnjoinedGroups_for_User

Conflicts:
	tavern/models.py
Merge pull request #45 from agiliq/Get_UnjoinedGroups_for_User

Get unjoined groups for user