[noise] Go implementation

[Jonathan Rudenberg]

> On Nov 16, 2015, at 3:22 AM, Trevor Perrin <trevp at trevp.net> wrote:
> 
> On Sun, Nov 15, 2015 at 2:20 PM, Jonathan Rudenberg
> <jonathan at titanous.com> wrote:
>> 
>> PSK implementation is working: https://github.com/titanous/noise/compare/psk
> 
> Looks great in general, but I think the PSK needs tweaking for the
> MixPresharedKey() step.
> 
> https://github.com/trevp/noise/blob/psk2/noise.md

Done! And the vectors from screech match.