repaired example

repaired element incompatibility (opening and closing tag) in example

examples/polymer.html

@@ -95,7 +95,7 @@ <h2>Future Date</h2>
     Time until (micro format):
     <time-until format="micro" datetime="2017-01-01T00:00:00.000Z">
       Oops! This browser doesn't support Web Components.
-    </time>
+    </time-until>
   </p>
   <script src="../dist/time-elements-legacy.js"></script>
 </body>