add categories to forum topics

app/views/forum_topics/show.html.erb

@@ -7,6 +7,8 @@
       <% end %>
     </h1>
 
+    <p class="info">Posted under <%= link_to @forum_topic.category_name, forum_topics_path(:search => {:category_id => @forum_topic.category_id}) %></p>
+
     <% if @forum_topic.is_locked? %>
       <div class="notice">
         <p>This topic has been locked.</p>