Slight overhaul to add oAuth

This is a pretty quick Pull Request and might need some further tweaking, but it uses oAuth to verify a user's credentials, allowing github-tree to be used with private repositories. This operates through https://oauth.io/ rather than having to use a server to handle the authentication. 

I have seen some issues come up related to caching, so right now it does have the popup for authentication appear every single load, which is probably annoying. I suspect the timeout for such sensitive data is higher for security purposes. 

Still, this should give us a decent platform to launch from for further improvements.