[WIP] Add a websocket endpoint to libchan

Implements a libchan server Receiver over HTTP2 over Websockets
over HTTP, and a client for connecting to said server.

signed-off-by: Clayton Coleman <ccoleman@redhat.com> (github: smarterclayton)
The ideal behavior you were mentioning here would be to allow the function to return, which will causing the handler to finish and the defered session.Close to be called. Problem is since the spdy framing is done inside the websocket, I am not sure how to propagate a "half-close" to a spdy session instead of a spdy stream.  The expected spdy behavior is any attempt to tear down the session should reset the underlying spdy streams, not put the streams in half-close.