Add Google Analytics.

doc/_templates/layout.html

@@ -0,0 +1,14 @@
+{% extends "!layout.html" %}
+
+{% block footer %}
+{{ super() }}
+<!-- Google 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','//www.google-analytics.com/analytics.js','ga');
+  ga('create', 'UA-20116650-4', 'cppformat.github.io');
+  ga('send', 'pageview');
+</script>
+{% endblock %}