docs($ionicModal): add docs for modal.removed and modal.hide

Closes #1320

js/angular/service/modal.js

@@ -38,6 +38,14 @@
  *   $scope.$on('$destroy', function() {
  *     $scope.modal.remove();
  *   });
+ *   // Execute action on hide modal 
+ *   $scope.$on('modal.hide', function() {
+ *     // Execute action
+ *   });
+ *   // Execute action on remove modal
+ *   $scope.$on('modal.removed', function() {
+ *     // Execute action
+ *   });
  * });
  * ```
  */