Room change sanity check

[tylerc]

Currently, the game client can change to any room it requests, no matter if this room isn't accessible from the current room, or even if the requested room doesn't exist. This should be stopped by the server.

Or better yet, maybe the client should have nothing to do with changing the room, and instead wait for the server to tell it to change rooms... We'd need a /news or /update method on the server for this methinks