Bitmex-trio-websocket

* Log websocket closure on errors.
* Update trio

Remote closure behaviour changed again. Closure will now result in a ConnectionClosed error being raised into the pipeline.
Listeners will simply be closed.

* Revert 0.13.1 error handling to 0.13.0. It is most likely preferable that all listeners are notified of websocket closure.
* Update slurry-websocket.

* Raising on all listeners seems a bit noisy. Now raises once from the context manager, if close code != 1000.
* Update dependencies.

New behaviour: If the websocket is closed remotely, bitmex-trio-websocket will now raise trio-websocket.ConnectionClosed,
and include the underlying reason for the closure, on all open listeners. Previously, listener generator functions would
simply end silently, and you would have to either assume that the websocket was remotely closed, or peek into the private
_websocket attribute to check the underlying websocket state.

* Check if the websocket is still open, before attempting to unsubscribe from tables. No sense talking to a dead phone line.