tweak styles for intro page

app/presenters/intro_presenter.rb

@@ -1,6 +1,6 @@
 class IntroPresenter
   def popular_tags
-    Tag.order("post_count desc").limit(8).map(&:name)
+    Tag.where("category in (3, 4)").order("post_count desc").limit(8).map(&:name)
   end
 
   def each

app/presenters/post_set_presenters/post.rb

@@ -23,25 +23,7 @@ module PostSetPresenters
     end
 
     def popular_tags
-      Cache.get("popular-tags", 1.hour) do
-        CurrentUser.scoped(User.admins.first, "127.0.0.1") do
-          n = 1
-          results = []
-
-          while results.empty? && n < 256
-            query = n.days.ago.strftime("date:>%Y-%m-%d")
-            results = RelatedTagCalculator.calculate_from_sample_to_array(query)
-            n *= 2
-          end
-
-          results.map! do |tag_name, recent_count|
-            tag = Tag.find_or_create_by_name(tag_name)
-            [tag_name, recent_count.to_f / tag.post_count.to_f]
-          end
-
-          results.sort_by! {|x| -x[1]}.map(&:first)
-        end
-      end
+      Tag.trending
     end
 
     def pattern_tags