Add models for User and Room

[priyanshsaxena]

Consider:

• Users can be registered or guest.
• Registered users must be given a username, other info should be minimal to start with.
• A room (or should we call it Match, or Game) should have number of rounds (times each player would get to deal), two teams (Red/Blue ?) and four players, and the score for each team.
• Each round is characterized by the highest bidder (whose partner has to open up the cards), the bid and the cards assigned to the players. What else do we need ?