fix(a): prevent Opera from incorrectly navigating on link click

we handle the navigation by ourselves, so we need to prevent the default action.

Opera ignores event.preventDefault() call so we must return false.

src/ng/directive/a.js

@@ -27,6 +27,7 @@ var htmlAnchorDirective = valueFn({
         // if we have no href url, then don't navigate anywhere.
         if (!element.attr('href')) {
           event.preventDefault();
+          return false; // Needed for opera
         }
       });
     }