Upgrading netty to 4.1.x

[aldemirenes]

There are breaking changes between 4.1 and 4.0 Most of the project start to use 4.1 and this creates classpath errors. It'll be good upgrading netty to 4.1.x

[mgenov]

It would be good to be added as latest version of grpc is using netty 4.1.x and this causes conflicts.