Add curated posts page.

Add a curated posts page at /explore/posts/curated. Curated posts are
the most favorited posts by contributor-level users (users with
unlimited upload permissions).

Also add an order:curated tag using for use in regular searches.

app/helpers/popular_posts_helper.rb

@@ -20,4 +20,14 @@ module PopularPostsHelper
       1.month.ago(date)
     end
   end
+
+  def date_range_description(date, scale, min_date, max_date)
+    if scale == "day"
+      date.strftime("%B %d, %Y")
+    elsif scale == "week"
+      "#{min_date.strftime("%B %d, %Y")} - #{max_date.strftime("%B %d, %Y")}"
+    elsif scale == "month"
+      date.strftime("%B %Y")
+    end
+  end
 end