[noise] NoiseSocket - next steps

[Alexey Ermishkin]

So, now I have what seems to be a working PoC
https://github.com/go-noisetls/noisetls with XX & IK support and negotiation

And a kind of protocol description
https://github.com/go-noisetls/noise_socket_spec/blob/master/noise_socket.md

My implementation also has padding & can send encrypted payloads in both
directions during the handshake.

I'm ready for criticism & further discussion :)