Simplify co-op page markup

Now we no longer have two columns of content.

_layouts/coop.html

@@ -13,16 +13,9 @@
       <a class="slice_subtitle" href="{{ page.website }}" target="_blank">{{ page.website }}</a>
     </section>
 
-    <div class="two-column">
-      <div class="two-column_left">
-      </div>
-
-      <div class="two-column_right">
-        <section>
-          <p>{{ content }}</p>
-        </section>
-      </div>
-    </div>
+    <section class="slice">
+      <p>{{ content }}</p>
+    </section>
 
     {% include footer.html %}
   </body>