package/python-redis: new package

The Python interface to the Redis key-value store.

https://github.com/andymccurdy/redis-py



Signed-off-by: Grzegorz Blach <grzegorz@blach.pl>
[Peter: hiredis is an optional runtime dependency, not build time]
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>