position tooltip in #site

Fixes  #7654. As the position may be calculated for some browser
differently because of the translate-Z hack.

IPython/html/templates/notebook.html

@@ -290,10 +290,10 b' data-notebook-path="{{notebook_path}}"'
 <div id="ipython-main-app">
     <div id="notebook_panel">
         <div id="notebook"></div>
+        <div id='tooltip' class='ipython_tooltip' style='display:none'></div>
     </div>
 </div>
 
-<div id='tooltip' class='ipython_tooltip' style='display:none'></div>
 
 {% endblock %}