@leporo thanks for your review.

I think we should use proven code to reduce development work, rather than copy it and maintain it by ourselves again, just like we use tornado io framework.
In general, the backward compatible is guaranteed by the author.

As for software license issues, we may need to add MIT License, [redis-py](https://pypi.python.org/pypi/redis/) is released under it.

Anyway, I understand your concerns about that the redis-py will be not backward compatible, so I close this patch.