Add post count to similar posts popup. Fix alignment.

app/serializers/basic_topic_serializer.rb

@@ -2,5 +2,5 @@ require_dependency 'age_words'
 
 # The most basic attributes of a topic that we need to create a link for it.
 class BasicTopicSerializer < ApplicationSerializer
-  attributes :id, :fancy_title, :slug
+  attributes :id, :fancy_title, :slug, :posts_count
 end

app/serializers/listable_topic_serializer.rb

@@ -3,7 +3,6 @@ require_dependency 'age_words'
 class ListableTopicSerializer < BasicTopicSerializer
 
   attributes :reply_count,
-             :posts_count,
              :highest_post_number,
              :image_url,
              :created_at,