add default collapse feature for layout

app/views/archives/index.html.erb

@@ -5,7 +5,7 @@
 %>
 <% if data["categories"].length == 1 %>
 <script>
-	$("#main-content .panel-collapse").addClass("in");
+	$("#main-content .panel-collapse").not('.default-collapse .panel-collapse').addClass("in");
 </script>
 <% end %>
 <% if total_pages > 1 %>