Issue #90 and PR #96 sought to promote Netty from the testing directory to normal src/main/java code.

As detailed in #96 I was historically reluctant to do this because of intermittent issues with Netty. Eventually I investigated these issues and corrected them in #133. As this was almost a year ago and I haven't seen any issues in any builds since then, I assume the fix worked and it's safe to promote Netty out of test as a result.