Adding ngModel.

look at this pull Request it implements the event ngModel.$setContext to especify the context should expression will be evaluated, example:

```javascript
mod.directive('myFancyInput', function() {
  return {
    require : 'ngModel',
    scope : { ... hash ...},
    link : function(scope, element, attrs, ngModel) {
      ngModel.$setContext(scope.$parent);
    }
  }
})
````