Add Google Analytics to measure site visitors (#314)

* Add Google Analytics to measure site visitors

Add the tracking script to the documentation template so we can know how
many people are visiting the docs and which pages they see the most.
The data are anonymous and we do not store cookies to track users in
other sites. This limits the amount of information we can get but is
much more ethical and less creepy.

* Add disclaimer about GA to footer

* Add link to google analytics docs

Author: leouieda

doc/_templates/footer.html

@@ -0,0 +1,16 @@
+{# Import the theme's layout. #}
+{% extends "!footer.html" %}
+
+{%- block extrafooter %}
+<p>
+Built with <a href="http://sphinx-doc.org/">Sphinx</a>
+using a <a href="https://github.com/rtfd/sphinx_rtd_theme">theme</a>
+provided by <a href="https://readthedocs.org">Read the Docs</a>
+</p>
+<p>
+This website uses Google Analytics to gather usage statistics.
+However, it does not use cookies or track you across different websites.
+Page view data are used to help us improve the site and provide an estimate of the
+software usage.
+</p>
+{% endblock %}

doc/_templates/layout.html

@@ -1,6 +1,22 @@
 {# Import the theme's layout. #}
 {% extends "!layout.html" %}
 
+{% block extrahead %}
+    <!-- Google Analytics tracking code -->
+    <!-- See https://developers.google.com/analytics/devguides/collection/analyticsjs/ for documentation. -->
+    <!-- 'storage': 'none' disables cookies -->
+    <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', 'UA-38125837-7', 'auto', {'storage': 'none'});
+      ga('set', 'anonymizeIp', true);
+      ga('send', 'pageview');
+    </script>
+{% endblock %}
+
 
 {% block htmltitle %}
     {% if title == '' or title == 'Home' %}

doc/conf.py

@@ -116,12 +116,14 @@
 pygments_style = "default"
 add_function_parentheses = False
 html_show_sourcelink = False
-html_show_sphinx = True
+html_show_sphinx = False
 html_show_copyright = True
 
 # Theme config
 html_theme = "sphinx_rtd_theme"
 html_theme_options = {}
+repository = "GenericMappingTools/pygmt"
+commit_link = f'<a href="https://github.com/GenericMappingTools/pygmt/commit/{ __commit__ }">{ __commit__[:7] }</a>'
 html_context = {
     "menu_links": [
         (
@@ -152,8 +154,9 @@
     "gallery_dir": dict(
         zip(sphinx_gallery_conf["gallery_dirs"], sphinx_gallery_conf["examples_dirs"])
     ),
-    "github_repo": "GenericMappingTools/pygmt",
+    "github_repo": repository,
     "github_version": "master",
+    "commit": commit_link,
 }