64284810 display error messages

* Removing PagesController because we aren't using it and you shouldn't write code because you *expect* to need it one day
* Root app endpoint is now `users#new` because we are starting users out at the signup page for now
* Invalid users trying to signup now are greeted with a single, coherent error message window
* Specs written for `#new` and `#create` actions in UsersController
* `users.js` handling invalid user creation now as well