Include pinned topics in category list.

- removes an (n+1) query for user data
- supports the preload store for the data to avoid a second request
- fix a bug where uncategorizes was reporting (0, 0, 0) for topics by week, month, year

db/migrate/20130528174147_add_rank_to_category_featured_topics.rb

@@ -0,0 +1,6 @@
+class AddRankToCategoryFeaturedTopics < ActiveRecord::Migration
+  def change
+    add_column :category_featured_topics, :rank, :integer, default: 0, null: false
+    add_index :category_featured_topics, [:category_id, :rank]
+  end
+end