Add permalink to GitHub power up

[Randy Tobias]

I apologize if this is the wrong place to post this, but i would find it extremely helpful if, for the GitHub power up, we could pick a repo and a branch, and be able to add a link to a specific line of code. This would function much like using the permalink option, but this could make it easier to user from the trello workflow (add power up, pick your repo, branch, line without having to leave trello). It could also still add the quick info about contributors and perform permission checks.