Finish user edit, update, index and destroy actions, add functionality that allows a user to be an admin and delete other
users, add an option to delete any user that is not the current user to the index page if the current user is an admin,
write integration tests for all of these features and have them passing at this time - App is at the end of chapter 9, before
the exercises have been attempted, ready to begin section 9.5 (Conclusion).