fix class names in popover live examples in docs

docs/_includes/js/popovers.html

@@ -73,8 +73,8 @@
 {% endhighlight %}
 
   <h4>Four directions</h4>
-  <div class="bs-example tooltip-demo">
-    <div class="bs-example-tooltips">
+  <div class="bs-example popover-demo">
+    <div class="bs-example-popovers">
       <button type="button" class="btn btn-default" data-container="body" data-toggle="popover" data-placement="left" data-content="Vivamus sagittis lacus vel augue laoreet rutrum faucibus.">
         Popover on left
       </button>