Revert changes to the default layout

and instead make a new "page" layout for markdown-based pages. This
avoids changing the HTML based pages which are using the "default"
layout currently.

content/governance.md

 ---
 title: Governance
-layout: default
+layout: page
 
 ---
 

layouts/default.html

 <%= render 'header' %>
 
 <div class="container">
-    <div class="col-md-12 doc-content">
   <%= yield %>
-    </div>
   <%= render 'container_footer' %>
 </div>
 

layouts/page.html

+<%= render 'header' %>
+
+<div class="container">
+  <div class="row">
+    <div class="col-md-12 doc-content">
+      <%= yield %>
+    </div>
+  </div>
+  <%= render 'container_footer' %>
+</div>
+
+<%= render 'footer' %>