feat(dropdownToggle): disable dropdown when it has the disabled class

Author: SanjoSolutions

src/dropdownToggle/dropdownToggle.js

@@ -31,7 +31,7 @@ angular.module('ui.bootstrap.dropdownToggle', []).directive('dropdownToggle', ['
           closeMenu();
         }
 
-        if (!elementWasOpen) {
+        if (!elementWasOpen && !element.hasClass('disabled') && !element.prop('disabled')) {
           element.parent().addClass('open');
           openElement = element;
           closeMenu = function (event) {
@@ -49,4 +49,4 @@ angular.module('ui.bootstrap.dropdownToggle', []).directive('dropdownToggle', ['
       });
     }
   };
-}]);
+}]);