add YAML options before-content and after-content

_layouts/post.html

@@ -31,6 +31,14 @@ layout: base
         </div>
       {% endif %}
 
+      {% if page.before-content %}
+        <div class="before-content">
+          {% for file in page.before-content %}
+            {% include {{ file }} %}
+          {% endfor %}
+        </div>
+      {% endif %}
+
       <article role="main" class="blog-post">
         {{ content }}
       </article>
@@ -44,6 +52,14 @@ layout: base
         </div>
       {% endif %}
 
+      {% if page.after-content %}
+        <div class="after-content">
+          {% for file in page.after-content %}
+            {% include {{ file }} %}
+          {% endfor %}
+        </div>
+      {% endif %}
+
       {% if page.social-share %}
         {% include social-share.html %}
       {% endif %}