Render form to comment topics before the comments

Just like we do in debates, proposals, ... We could argue whether it's
better to have the form before or after the list of comments, but at the
very least we should have some sort of consistency.

app/views/topics/_comments.html.erb

@@ -4,14 +4,15 @@
     <div id="comments" class="small-12 column">
       <%= render "shared/wide_order_selector", i18n_namespace: "comments" %>
 
-      <%= render "comments/comment_list", comments: @comment_tree.root_comments %>
-      <%= paginate @comment_tree.root_comments %>
-
       <% if user_signed_in? %>
         <%= render "comments/form", { commentable: @topic, parent_id: nil } %>
       <% else %>
+        <br>
         <%= render "shared/login_to_comment" %>
       <% end %>
+
+      <%= render "comments/comment_list", comments: @comment_tree.root_comments %>
+      <%= paginate @comment_tree.root_comments %>
     </div>
   </div>
 <% end %>