Updated to work with websocket-driver instead of websocket-protocol

Hi,

The [websocket-protocol](http://github.com/faye/websocket-protocol-ruby) gem seems to have been superseded by websocket-driver (the previous link redirects to the websocket-driver page). It is mostly API compatible with websocket-protocol, so upgrading to be able to support the more recent development on that end was quite easy. Attached is my PR which updates the gem to work with websocket-driver.

I've test the client example and it seems to work as it should with the changes.