remove System.out instead of logger.info
update groupId to com.qunar.db, version 1.0.0
Optimize ZkClient:
When Session Expired, call reopenZkConnection() method.

Here is a problem:
ZkClient catches ConnectionLossException, whether to call
reopenZkConnection?

If call, the NODE_REFRESH will be installed twice.
First, call reopenZkConnection().
Second, last session expired, ZkWatcher's process will call
reopenZkConnection again!

In this version, I don't call reopenZkConnection when I catches
ConnectionLossException!