Remove ZKServiceWrapper.
Resolve the race in shutting down and correctly force flush logs.
- Sleep for 1 second before stopping kafka server to allow clients to have chance to fetch last logs.
- Stop kafka server in finally block.
- Remove System.out
Merge pull request #56 from continuuity/feature/remove-zkwrapper

Remove buggy ZKServiceWrapper. Force log flush when stop rather than depending on Appender stop.