WebSocket: allow "options" to be the 3rd argument
WebSocket: allow "options" to be the 3rd argument

Currently the 2nd argument (`protocols`) is ignored.

Eventually the "selected" protocol should be set as `socket.protocol`,
depending on that the WebSocket server responds with support for, but
that's for another commit...

Part of #227.

guymguym/ws,karatheodory/ws,websockets/ws