use RedisStore, change auth level, sort guests

Now there are 2 auth methods:
- ensureAuthenticated - checks if the user is authenticated (logged in with facebook)
- ensureUserIsAdmin - checks if the user authenticated is an admin

Using redisStore for session management. The built-in store leaks memory and is not production ready.

Add sorting to the guestList. Sort is based on a custom method that splits the name property of a guest object and returns the surname (split by ' ' and return last element).