add disqus comments as per hpstr theme

_includes/_scripts.html

@@ -17,4 +17,7 @@
     var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(ga, s);
   })();
 </script>
+{% endif %}
+{% if page.comments %}
+  {% include _disqus_comments.html %}
 {% endif %}