Change .html.twig to .html

Change other file extensions for consistency.

source/_layouts/post.html

@@ -0,0 +1,28 @@
+{% extends 'default' %}
+
+{% block content_wrapper %}
+  <div class="col-md-10">
+
+    {% include 'post-header' %}
+    {% block content %}{% endblock %}
+
+    {% if page.tags %}
+      <p class="tags">
+        Tags:
+        {% for tag in page.tags %}
+          <a href="{{ site.url }}/blog/tags/{{ tag|url_encode(true) }}">{{ tag }}</a>{% if not loop.last %}, {% endif %}
+        {% endfor %}
+      </p>
+    {% endif %}
+
+    {% include 'about-author' %}
+
+    {% if page.next_post or page.previous_post %}
+      <ul>
+        {% if page.next_post %}<li>Next post: <a href="{{ page.next_post.url }}">{{ page.next_post.title }}</a></li>{% endif %}
+        {% if page.previous_post %}<li>Previous post: <a href="{{ page.previous_post.url }}">{{ page.previous_post.title }}</a></li>{% endif %}
+      </ul>
+    {% endif %}
+
+  </div>
+{% endblock %}