WebSocket.send_bytes is a coroutine as of aiohttp 3.0 changing transp…

WebSocket.send_bytes is a coroutine as of aiohttp 3.0 changing transport.write to await the coroutine if necessary.

docs: fixed missing references

* Allows building documentation in strict mode with:
  `sphinx-build -qnNW docs docs/_build/html`  (closes #9)

Async dsl