Attempt to fix usage in application.rb

I fixed usage in `application.rb` (#32, #44), by reverting a change. **But** I broke some features in the process (changing the constant) by hooking directly into ActiveSupport.

Does anyone have any ideas how I could hook in earlier (before `application.rb` is loaded), but preserve the initializer order (loading after `:load_custom_rails_config`).

/cc @railsjedi