Removed invalid assertions
Added toString() for debugging
Adding logging messages
Fixed not to call handler.onUpdate when deltaUpdates < 1
Removed unnecessary logging
Fixed pipeline
Fixed the variable name of MixClientHandler
Fixed to use custom encoder/decoder. 
hadoop.io.Text is not Serializable with the netty's ObjectEncoder.
Fixed a bug for multiclass classification
Fixed to set SO_KEEPALIVE in server as well
Fix a bug in pipeline
Fixed to sent out the packet in the worker
Added a comment
Fixed to send responseMsg asynchronously in MixServerHandler