Fix title on all pages.

Author: mallamanis

_includes/head.html

@@ -13,6 +13,14 @@
   <meta http-equiv="content-type" content="text/html; charset=utf-8">
   <meta name="keywords" content="machine learning, source code, big code, naturalness, software engineering, programming languages">
 
+  <title>
+    {% if page.title == "Home" %}
+      {{ site.title }} &middot; {{ site.tagline }}
+    {% else %}
+      {{ page.title }} &middot; {{ site.title }}
+    {% endif %}
+  </title>
+
   <!-- Enable responsiveness on mobile devices-->
   <meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1">