Add new server list filter to support making only a subset of all servers available for the load balancer.
Merge commit '3d6e4f0ba6a7d7f7f705d4b493937f0d7c18363e'
Added more javadoc and copyright.
Track total failures count for client upon exception.
Merge pull request #26 from allenxwang/master

Add subset filter for server list