add YAML options before-content and after-content

_layouts/default.html

@@ -5,5 +5,21 @@ layout: base
 <div class="intro-header"></div>
 
 <div role="main" class="{% if page.full-width %} container-fluid {% else %} container-md {% endif %}">
+  {% if page.before-content %}
+    <div class="before-content">
+      {% for file in page.before-content %}
+        {% include {{ file }} %}
+      {% endfor %}
+    </div>
+  {% endif %}
+
   {{ content }}
+
+  {% if page.after-content %}
+    <div class="after-content">
+      {% for file in page.after-content %}
+        {% include {{ file }} %}
+      {% endfor %}
+    </div>
+  {% endif %}
 </div>