Peer disconnected in room pr

Disconnected Peer will be remove in the peer set (rooms[roomID]) in this PR. Because the issue 35 https://github.com/t-mullen/simple-signal/issues/35 We change the output simple-signal-client.js by hand.

@t-mullen https://github.com/t-mullen/simple-signal/issues/35 has been solved by this commit https://github.com/t-mullen/simple-signal/pull/36/commits/a5a84acc62dde7d97d7773e1dd6718bd8960735b And finally, peer disconnected in the room and switch room can work correctly.

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.
https://github.com/t-mullen/simple-signal/pull/36/commits/703016cde31d1e9ef822b3324edb3e2b8d3bf3e7