FEATURE: change group default tracking level to tracking (database changes)

db/migrate/20160127105314_change_default_notification_level_on_groups.rb

@@ -0,0 +1,6 @@
+class ChangeDefaultNotificationLevelOnGroups < ActiveRecord::Migration
+  def change
+    execute "UPDATE group_users SET notification_level = 2"
+    change_column :group_users, :notification_level, :integer, null: false, default: 2
+  end
+end