First cut of ZK client
Added test cases. Also make expireRewatch don't need a RetryStrategy.
Added bunch of RetryStrategies and test cases.
Refactor and adding some more docs.
Added bunch of javadocs and some new test cases.
Simplify implementation and reduce number of callback objects created.
Also added test cases.
More javadocs, address review comments.
Merge pull request #1 from chtyim/feature/v0.1