Adds pre-commit hook, hook config script, and relevant README

The pre-commit hook will automatically gofmt code in place, warning you about any changes. It will also fail to commit if either golint or go vet fails.

As git hooks cannot be added to a repository in a way that automatically applies them, `configure-hooks.sh` can be ran to link this pre-commit hook.

@dmp42 @stevvooe 
Any reason to deviate from the circleci syntax? (eg: maybe it would make maintenance easier down the road if they were "closer"?)