Fix for netty websocket implementation

Updated NettyAsyncHttpProvider and NettyWebSocket to properly handle web
socket frames and callbacks
Merge pull request #217 from slandelle/master

Minor clean up after PR #214
Merge pull request #215 from RickBullotta/master

Fix for netty websocket implementation
Allows to configure Netty NioClientSocketChannelFactory
Merge pull request #219 from andekaputra/master

Allow to configure NioClientSocketChannelFactory to NettyAsyncHttpProvider