Remove extensions from _includes to simplify naming

_pages/tag-archive.html

@@ -4,13 +4,13 @@ permalink: /tag-archive/
 title: "Posts by Tags"
 ---
 
-{% include absolute-url.liquid %}
-{% include group-by-array.html collection=site.posts field='tags' %}
+{% include base_path %}
+{% include group-by-array collection=site.posts field='tags' %}
 
 {% for tag in group_names %}
   {% assign posts = group_items[forloop.index0] %}
   <h3>{{ tag }}</h3>
   {% for post in posts %}
-    {% include archive-list-single.html %}
+    {% include archive-list-single %}
   {% endfor %}
 {% endfor %}