Add mget/set to Distributed

I was testing the distributed redis with an app that I have and noticed the mget and mset didn't work, obviously because you do not know in which node this should be set. Then I saw the impementation for Redis::Distributed#del and thought we can do something similar for this.
I'm not sure if you want this or it is intentionally left out so anybody do this on their own if needed.
Either way here it is.