Modify google analytics code in documentation

doc/.templates/layout.html

@@ -7,6 +7,9 @@
 {% block extrahead %}
     <script type="text/javascript">
       var _gaq = _gaq || [];
+      var pluginUrl =
+        '//www.google-analytics.com/plugins/ga/inpage_linkid.js';
+      _gaq.push(['_require', 'inpage_linkid', pluginUrl]);
       _gaq.push(['_setAccount', 'UA-248813-2']);
       _gaq.push(['_setDomainName', '.skewed.de']);
       _gaq.push(['_trackPageview']);