fix(checkbox): labels with links throw exception in IE11

Author: Splaktar

src/components/checkbox/checkbox.js

@@ -111,7 +111,8 @@ function MdCheckboxDirective(inputDirective, $mdAria, $mdConstant, $mdTheming, $
         attr.$set('aria-labelledby', labelId);
 
         var label = element.children()[1];
-        label.remove();
+        // Use jQLite here since ChildNode.remove() is not supported in IE11.
+        angular.element(label).remove();
         label.removeAttribute('ng-transclude');
         label.className = 'md-checkbox-link-label';
         label.setAttribute('id', labelId);