Workflow refactor

This change, combined with Carly's User Profile Editing branch completes the vendor registration workflow refactor. Changes include an added splash screen, as well as the ability to register as both a customer and a vendor directly through the app. (This means that a script is no longer required for us to turn accounts into Vendors. We'll instead have to write a script to flip the is_active flag on new vendors, or do the superuser view we've talked about).