netty transport: add ssl support.
netty transport: set access levels of inner classes properly.
Merge pull request #132 from m1ch1/ssl

netty transport: add ssl support.
Change the cluster configuration of AckProcessor at correct time.
Fixed the bug and more logging messages for AckProcessor.
Merge pull request #131 from EasonLiao/ack_cluster_config

Change the cluster configuration of AckProcessor at correct time.
Add RollingLog implementation.
Merge pull request #133 from EasonLiao/rolling_log

Add RollingLog implementation.