Add Cowboy 0.8.x Support - Clean Patch Series

Clean patch series against current master to support cowboy 0.8.3.
It passes all unit-test from sockjs-protocol-0.3.3.py cleanly.

(except for WebsocketHixie76 where support got removed in cowboy 0.8)
see https://github.com/extend/cowboy/blob/master/CHANGELOG.md