Let user specify HTTP proxy port #69
Description
Some platforms (like Heroku) require that apps bind to a port specified by an environment variable. That means I can't deploy apps using this client to Heroku, as this client (as far as I know) always tries to bind to port 80.
This create_connection call defaults to port 80. It'd be nice if we could pass additional options to be forwarded to this underlying create_connection call - that library accepts an option to specify port like so:
ws.connect("ws://example.com/websocket", http_proxy_host="proxy_host_name", http_proxy_port=3128)