Load danbooru_default_config.rb earlier.

Load danbooru_default_config.rb inside application.rb instead of in an
initializer so that it's available as soon as possible.

config/initializers/danbooru_config.rb

@@ -1,10 +0,0 @@
-require "#{Rails.root}/config/danbooru_default_config"
-require "#{Rails.root}/config/danbooru_local_config"
-
-module Danbooru
-  def config
-    @configuration ||= EnvironmentConfiguration.new
-  end
-
-  module_function :config
-end