Allow heroku to interact with private repos

I've write this down because I was having issues with Go and my private packages.
This one makes sure you have everything to allow Heroku to clone private stuff you might have in your application.

This is really great when you have private dependencies. Just add the GitHub token and good bye issues. :).

https://gist.github.com/elcuervo/be15b1f47d270c11fc61