Upgrade to Netty 4 for better performance and more flexible assignment of Threads
netty4 fixes
test fixes
using getBodyBuffer() to getBodyBufferCopy() in ServerMessageImpl.toString()

getBodyBuffer() will alter the readerIndex of the internal buffer of the message. This will
cause problem if the toString() is called before the message is marshaled to the netty.
Merge pull request #1374 from andytaylor/master

netty4 work