Netty dependency version is vulnerable #423

Hey folks,

You are using a vulnerable version of Netty with an impressive 9.8/10 criticality score. Suggest patching ASAP to 4.1.50.Final which should have binary compatibility as they are on modified semver

I'd submit a PR but I'm awaiting a confirmation on signing the Google CLA and I assume you want to move fast here. Tests seemed to pass in my local fork though

Cheers!