Add golint for Golang style checking

This is utility put out by the Golang team to check style violations. It
reminds you to document your public fields and functions among other
helpful things.

This adds a pre-commit hook to run golint, if installed, by default on
all change .go source files.

Verified locally by building a gem and running on a Go project I'm
working on.

Change-Id: Ia6f03c9b08c865f6ace5d52d9016138307cf60bd
Reviewed-on: http://gerrit.causes.com/39122
Tested-by: jenkins <jenkins@causes.com>
Reviewed-by: Shane da Silva <shane.dasilva@brigade.com>