UDP audio support

[MarcusWolschon]

https://github.com/layeh/gumble/blob/master/gumble/handlers.go#L79
The decoding, waiting for the lock and processing of the decoded audio buffer should probably be done asynchronously and not block the handling of further UDP packets.

[ghost]

Ideally, gumble would implement UDP support, and the UDP connection would be running from a different go routine. I have a local branch that nearly implements UDP support. I can push that dev branch later today if you want to try tackling it, @MarcusWolschon.

[MarcusWolschon]

I've never coded in golang yet.

[dchote]

I'd love to see UDP support

[ghost]

I just pushed what I was playing around with to the udp branch