Change xid and epoch of Zxid from 4 bytes to 8 bytes.
Fixed cluter_config format.
Merge pull request #117 from EasonLiao/fix_clusterconfig_file

clean up cluster_config format
Merge pull request #121 from EasonLiao/fix_zxid_length

change epoch and xid to 64-bit int
Merge pull request #140 from EasonLiao/master

Caches cluster configuration.
Fix the bug in AckProcessor.
Merge pull request #141 from EasonLiao/master

Fix the bug in AckProcessor.
Add flush operation.
Remove maven-site plugin.
Merge pull request #146 from EasonLiao/fix_maven

Remove maven-site plugin.
Merge pull request #142 from EasonLiao/add_sync

Add sync operation.
Use Semaphore to avoid the internal queues grow infinitely.