Kazoo 882 - Update cowboy

I've upgraded cowboy to 0.8.4, and updated Crossbar, Fax, and the Whistle Media lib to use the new cowboy_req module (replaced cowboy_http_req). I've tested most of the Crossbar APIs, and checked that proxying media to FreeSWITCH works again. I don't have a Fax setup to test, but the Fax changes were minimal and should work.

Crossbar SSL handling was updated, as well as proper shutdown of API servers when the Crossbar whapp is stopped.