Moving Zookeeper classes into api.
- Expose discovery service to WeaveContext and WeaveController
- Fix a bug in ZKDiscoveryService
  - If the node is created after the first call to discover(), it will fail.
Refactor ZKClient and ZKClientService
Namespace the ZK with the application name as well.
Register discovery service under the app name, not under run id.
Move DiscoveryService package.
Moving classes
Refactor classes and update docs and style.
Merge pull request #9 from chtyim/feature/v0.1

More features for the first release