Initial hook up of server side of settings

Server-side:
 * Add CurrentUserSerializer
 * Add CurrentUserController
 * Pluralize route to /current_users because Ember is fucking retarded
   and can't into singular objects
Client-side:
 * Add CurrentUser model to clientside (prefixed with zz_ to put it
   after User model in concatenation)
 * Add SettingsRoute to Ember
 * Tweak settings.hbs to use the proxied model instead of currentUser