Use controllerAs syntax to obviate use of $scope

By making reference to the AboutCtrl as main, rather than refer to
various objects on `$scope`, we can instead simply store them on a
reference to the controller using `this`. This removes the need to
inject `$scope` as a dependency and makes for cleaner controller code.
Pass in AwesomeThing service to controller

Pull out the business logic of awesome things from the controller and
place it into an injected service object.