Add support for Google Analytics to theme. (#411)

* Add support for Google Analytics to theme.

This setting has actually existed in the default config since the original version,
but doesn't currently work.
This fixes that and supports GA if it's set.

* Add docs around analytics_id

* Do not conflict with RTD insertion of analytics script

* Remove dupliate analytics_id

* Add analytics_id to the configuration in its new place

docs/configuring.rst

@@ -19,7 +19,7 @@ file of this repository, and can be defined in your project's ``conf.py`` via
 
     html_theme_options = {
         'canonical_url': '',
-        'analytics_id': '',
+        'analytics_id': 'UA-XXXXXXX-1',  #  Provided by Google in your dashboard
         'logo_only': False,
         'display_version': True,
         'prev_next_buttons_location': 'bottom',

sphinx_rtd_theme/layout.html

@@ -221,6 +221,23 @@
       });
   </script>
 
+  {# Do not conflict with RTD insertion of analytics script #}
+  {% if not READTHEDOCS %}
+    {% if theme_analytics_id %}
+    <!-- Theme Analytics -->
+    <script>
+    (function(i,s,o,g,r,a,m){i['GoogleAnalyticsObject']=r;i[r]=i[r]||function(){
+      (i[r].q=i[r].q||[]).push(arguments)},i[r].l=1*new Date();a=s.createElement(o),
+      m=s.getElementsByTagName(o)[0];a.async=1;a.src=g;m.parentNode.insertBefore(a,m)
+    })(window,document,'script','https://www.google-analytics.com/analytics.js','ga');
+
+    ga('create', '{{ theme_analytics_id }}', 'auto');
+    ga('send', 'pageview');
+    </script>
+
+    {% endif %}
+  {% endif %}
+
   {%- block footer %} {% endblock %}
 
 </body>