Update Go language icon

[ClydeDz]

Name: Go lang
Official resources for icon and color: https://blog.golang.org/go-brand and this brand book

[birjj]

There actually was some discussion on this in the original PR. The consensus seemed to be that, since it's been 4 months (at the time, now 1 year) since they published the new design and they haven't really started using it anywhere, we'd stick with the gopher for now and update at a later time when they start using the new design as their actual brand. As far as I can see that hasn't happened yet.

I'm open for discussion on the topic though.

[fallsimply]

Go now uses the new go logo on thier website so the time to update is now