Brew Config: Go support

Adds a dash of Go support to the Brew Config to accompany the recent wider language support @mistydemeo weaved in.

Relates to this [comment](https://github.com/Homebrew/homebrew/issues/32014#issuecomment
-54135658).

Produces the output:

```
Go: /usr/local/bin/go => /usr/local/Cellar/go/1.3.1/libexec/bin/go
GoPath: /Users/Bob/go
```
As a counterpoint, the reason we are interested in the location of perl/python/ruby is that we support installs that exist outside of Homebrew. We don't support non-Homebrew go installs, and always add a direct `depends_on "go"` to formula that use it, so I'm not sure if this is valuable.