improves html structure for comments on debates and proposals

app/views/debates/show.html.erb

@@ -1,6 +1,6 @@
 <% provide :title do %><%= @debate.title %><% end %>
 <% cache [locale_and_user_status(@debate), @debate, @debate.author, Flag.flagged?(current_user, @debate), @debate_votes] do %>
-  <section class="debate-show">
+  <div class="debate-show">
     <div id="<%= dom_id(@debate) %>" class="row">
       <div class="small-12 medium-9 column">
         <%= render "shared/back_link" %>
@@ -59,7 +59,7 @@
           <% end %>
         </div>
     </div>
-  </section>
+  </div>
 <% end %>
 
 <%= render "comments" %>