Peer disconnected in room pr

[milochen0418]

Disconnected Peer will be remove in the peer set (rooms[roomID]) in this PR.
Because the issue 35
#35
We change the output simple-signal-client.js by hand.

[milochen0418]

@t-mullen
#35 has been solved by this commit a5a84ac
And finally, peer disconnected in the room and switch room can work correctly.

[milochen0418]

It's look like that peer.on('error') cannot catched all RTCErrorEvent in this case.
Some ERR_DATA_CHANNEL RTCErrorEvent cannot be catched right now,
so just to add how to stop throwing RTCErrorEvent in README and the one who follow this document can make a stable demo.
703016c