debugging websocket connections

- add debug statement at the very beginning of a web socket request
- add debug statement in open, indicating that the connection has been accepted
- add timeout, so failed or slow kernel_info doesn't cause the request to never get a response
- don't send kernel_info_request before authenticating the request

The last one required some icky coroutine shenanigans because of our subclass structure, but it should work fine.

ping @takluyver