Data Rebalancing

[ashwanthkumar]

Add ability for the cluster to

• scale out - addition of new nodes
• scale down - nodes going down.
• Anti Entropy - Refer #50 for more details

Tasks

• [ ] It's relatively easy to do data rebalancing with ConsistentHashRing, but given the generic nature of the RoutingStrategy. We need to decide on the interactions of Rebalancer with that of RoutingStrategy
• [ ] Implement / integrate membership with the Server. Once we've Membership, think about how would it integrate with Partitioner / RoutingStrategy for maintaining the list of nodes.

Dependencies

• [ ] While re-balancing we need to know what keys to migrate which needs an Anti-entropy implementation #50