now emits a wizard:stepChange event when the step changes

This will emit an event on $scope with the wizard:stepChanged event. Since an isolate scope is created for the directive, you can listen to $rootScope for the event change as below:

```javascript
$rootScope.$on('wizard:stepChanged', function(event, data) {
  data.step; // the step that changed
  data.index; // the index of the step that changed
});
```