Reorganized initializers a bit to enable better hooks for common cases without the need for Railtie. Specifically, the following hooks were added:

* before_configuration: this hook is run immediately after the Application class 
  comes into existence, but before the user has added any configuration. This is
  the appropriate place to set configuration for your plugin
* before_initialize: This is run after all of the user's configuration has completed,
  but before any initializers have begun (in other words, it runs right after
  config/environments/{development,production,test}.rb)
* after_initialize: This is run after all of the initializers have run. It is an
  appropriate place for forking in a preforking setup

Each of these hooks may be used via ActiveSupport.on_load(name) { }. In all these cases, the context inside the block will be the Application object. This means that for simple cases, you can use these hooks without needing to create a Railtie.