Initial app skeleton with github authentication working.

@dangoor 

No styling or actual upload functionality--just enough to make sure basic authentication works.

I'll send you a link to a set of config files you can use for testing if you don't feel like setting up your own GitHub app and self-signed cert :) If you use those, everything should just work at `localhost:4040` since I have the callback URL set that way in the GitHub app settings.

I'm almost not sure that the unit tests for the routes are worth it since they're so simple...let me know if you think I should just remove them.

Note that I'm using the numeric github ID as our internal user key instead of the username, since people can actually change their username. Does that make sense? For now I'm just showing that raw ID in the web page--we can use their real username for display purposes later.