Migrate from Java Nio to Netty

[NyxCode]

Currently, Kryonet uses the nio library of java. It does its job, but, In my opinion, it suffers from poor maintainability and performance. If we migrated to Netty, we would get

• better, more maintainable code
• better performance, especially on Linux or Mac using native transport

In the next few weeks, I'll look into it and submit a pull request. In the mean time, I would appreciate if we could discuss this topic here.

[NyxCode]

Also, I noticed that implementing SSL would be easy after migrating...

[NathanSweet]

I experimented with this some time ago:
https://github.com/EsotericSoftware/kryonetty
Supporting all the same features as KryoNet would take some work.