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
```
Perhaps we just want this in `doctor` instead?