Persistent rooms

[Fauntleroy]

Store rooms in the database so they persist across server reloads.

• [ ] Add database model for rooms
• [ ] Integrate room model into current room creation flow
• [ ] Rooms can be named
• [ ] Use "starttime delta" for syncing clients (to eliminate server state)
• [ ] Handle socket.io connections outside of room model
• [ ] Figure out how to handle presences in a distributed socket.io cluster

[Fauntleroy]

This is now a top priority, since Heroku shuts down the server if there haven't been http requests for a while.