updated upgrade page to reflect popover changes

docs/upgrading.html

@@ -241,6 +241,10 @@
   <div class="page-header">
     <h1>Javascript plugins</h1>
   </div>
+  <h3>Popovers</h3>
+  <ul>
+    <li>Child elements now properly namespaced: <code>.title</code> to <code>.popover-title</code>, <code>.inner</code> to <code>.popover-inner</code>, and <code>.content</code> to <code>.popover-content</code>.</li>
+  </ul>
 </section>