finish cleaning up ie 7-8 support

docs/index.html

@@ -545,6 +545,7 @@
           </tr>
         </tbody>
       </table>
+      <p><strong>Note:</strong> Zebra-striping is a progressive enhancement not available for older browsers like IE8 and below.</p>
 <pre class="prettyprint linenums">
 &lt;table class="common-table zebra-striped"&gt;
 ...