[Issue 29] Play multiple games

Solve #29 

### Given two users Marshall and Jessica have logged in the game
![screen shot 2014-08-04 at 10 48 01 am](https://cloud.githubusercontent.com/assets/806135/3799577/0b6c4192-1bef-11e4-887b-9d97657df969.png)

### Marshall creates a new game, he directly gets into the *pregame* zone, and Jessica can see that there is one game she can join
![screen shot 2014-08-04 at 10 48 12 am](https://cloud.githubusercontent.com/assets/806135/3799588/2395f7cc-1bef-11e4-9d21-8196d7778af8.png)

### Jessica joins the game, and Marshall can start the game
![screen shot 2014-08-04 at 10 48 19 am](https://cloud.githubusercontent.com/assets/806135/3799602/43df45c4-1bef-11e4-8318-2bc759629103.png)

### Marshall can start a game, and play normally
![screen shot 2014-08-04 at 10 48 26 am](https://cloud.githubusercontent.com/assets/806135/3799616/5c08d700-1bef-11e4-8935-dadf409769dd.png)

### In the end, the scores are displayed properly
![screen shot 2014-08-04 at 10 48 57 am](https://cloud.githubusercontent.com/assets/806135/3799621/6c27af1c-1bef-11e4-96b1-3a9839ba9242.png)