cowboy-0.8.* support for hell_http_listener and hello_sockjs_listener

Hi all,

i removed old pull requests, cleaned code and sent again. Here is support for cowboy-0.8.* for `hello_http_listener` and `hello_sockjs_listener`.

Changes:

  * `cowboy_req` everywhere instead cowboy_http_req.
  * New dispatch.
  * `cowboy_req:peer_addr/2` was removed but we use it in `hello_http_listener:req_transport_params/2`.
  * Lowercase header names - https://github.com/extend/cowboy/blob/master/guide/internals.md#lowercase-header-names