Superusers

This branch adds superusers to beLocal! Now, if you sign up as either a vendor or a customer and run `./scripts/addSuperUser.py` with your userID set, you will be added to the system as a superuser, allowing you to activate/deactivate vendor accounts in the system.

While working on this, I uncovered an interesting bug, which after some consideration, I think may actually be a feature: When a customer signs up, we actually create a Vendor object for them in the database, but this remains hidden due to the user.is_staff flag being set to False. I was originally going to remove this behaviour, but I thought that if we have a customer (who has already liked, say, 30 products) who wants to become a vendor, we should have the ability to turn them into a vendor account (by changing use.is_staff to True) without having to delete and recreate their account. What are everyone else's thoughts on this?

This pull request also includes Carly's M2 UI changes.
We can change this back if you guys would like, but the new colour is starting to grow on me.