Replace ordergroup.account_updated with non database attr.

db/migrate/20121230142516_remove_account_updated_from_ordergroups.rb

@@ -0,0 +1,9 @@
+class RemoveAccountUpdatedFromOrdergroups < ActiveRecord::Migration
+  def up
+    remove_column :groups, :account_updated
+  end
+
+  def down
+    add_column :groups, :account_updated, :datetime
+  end
+end