Merge pull request #66 from yohanboniface/hashfield

Refactoring of indexing, and new Hashfield
Better check for existing connection

This little commit is needed because of a recent change in redis-py: they added a `__len__` method to the Pipeline object, so a `if` will call this `__len__` method, which will return the number of waiting commands, which is `0` the first time, so in our case, the connection would be recreated, and we wouldn't be in a pipeline anymore...
Merge remote-tracking branch 'origin/master' into RIP_cache