Python3 compatibility

I used the `future` python module with its `futurize` command.

You can read the detail of the porting:

https://gist.github.com/twidi/4393191dccbc47fd9549#file-porting-redis-limpyd-to-python3-md
Just curious: does that imply that it's > 3.4, i.e. 3.3 not supported?