add test case for alert anchor close button

tests/components.html

@@ -2200,8 +2200,8 @@
         </div>
 
         <div class="bs-example">
-          <div class="alert alert-warning">
-            <button type="button" class="close" data-dismiss="alert">×</button>
+          <div class="alert alert-dismissable alert-warning">
+            <a class="close" data-dismiss="alert">×</a>
             <strong>Warning!</strong> Best check yo self, you're not looking too good.
           </div>
         </div>