cluster support #58
Description
Redis cluster support would be fantastic.
Cluster support can be implemented as a wrapper to the underlying connection library so this doesn't need to be implemented in eredis for exredis to work with it.
For example an Erlang wrapper supporting cluster: https://github.com/adrienmo/eredis_cluster
The reference ruby implementation is also simply a wrapper: https://github.com/antirez/redis-rb-cluster