Move the user queryset into the AppMixin
Add columns to the admin for Visions
Use the caching backend for session storage on dotcloud
Add super-secret ally signup page

- Add an endpoint that Django recognizes for making a user an ally
- Add a template for the ally signup page
- Add a handlebars helper for checking whether the current user is in a given group
- Add a handlebars helper for getting the CSRF token
- Add a getCookie method to utils
Change the 'authenticated' helper to 'if_authenticated' for consistency