Python-engineio-v3

- Correct generation of binary xhr2 packets ([commit](https://github.com/miguelgrinberg/python-engineio/commit/5e5e0a34faa218de32b5bf7a2358d12a3fd6493d))
- Do not write binary packets to the log ([commit](https://github.com/miguelgrinberg/python-engineio/commit/d338ee8787738aab7b7b2fcac9b31127dcb2e9b1))
- Hopefully addressed some tests that fail intermittently on travis ([commit](https://github.com/miguelgrinberg/python-engineio/commit/27bc79f91ad32a90f6f3ea8bd87cead8f4a14f41))

- Dispose of disconnected sockets ([commit](https://github.com/miguelgrinberg/python-engineio/commit/08c518db6c6dd12d81890cd6239113cfd84e9eec))
- disable imports warning in flake8 ([commit](https://github.com/miguelgrinberg/python-engineio/commit/e3badf30f89e4981ed419cf645ccec976370c376))

- Graceful failure when websocket is request and the async mode does not support it ([commit](https://github.com/miguelgrinberg/python-engineio/commit/2a5cdf289d2f1af97270f3bbf58669a507aecb9c))

- additional eventlet unit test ([commit](https://github.com/miguelgrinberg/python-engineio/commit/abd54e58d274355d961ed9272d7b7fda9e3ef9fc))
- Update tests to correspond with flake8 ([commit](https://github.com/miguelgrinberg/python-engineio/commit/d1969d6bc016b0e3dc66df7eeb30a9c76debc6b6)) (thanks **Artemiy Rodionov**!)
- Fix eventlet wsgi websocket __call__ return [12](https://github.com/miguelgrinberg/python-engineio/issues/12) ([commit](https://github.com/miguelgrinberg/python-engineio/commit/3f8ecccd40c3f05ef966a6f7e0e2953dc992dfa6)) (thanks **Artemiy Rodionov**!)

- Revert "_websocket_handler waits on writer even after the socket is closed" [11](https://github.com/miguelgrinberg/python-engineio/issues/11) ([commit](https://github.com/miguelgrinberg/python-engineio/commit/a4ffc8e916aabdc96b0cc7bb5262baf8bd39c661))