because `config/application.rb` is not yet loaded in `ActiveSupport.on_load`.
I can't find a way to configure ability of auto_locale  in this timing.

so if I want to include in `on_load`, `auto_locale` method should be like this,

```ruby
  def auto_locale
      I18n.locale =  http_accept_language.compatible_language_from(I18n.available_locales) if HttpAcceptLanguage.config.auto_locale?
  end 
```

but i think it it not so cool, because auto_locale will be called always if you don't want to do.