Ensure coordinator is able to release locks of a leaving member.
Add failover test for DistributedLockManager.
Fix critical bugs in DifferentialSynchronizationStrategy.
Throw ISE if selectAll query has no results.
Modify CommandDispatcher api to use CommandResponse abstraction.
This allows users of the api to distiguish between sender vs receiver failures.
Merge pull request #79 from pferraro/3.0

Ensure coordinator is able to release locks of a leaving member.