changes to the exception_notification plugin

first off, this thing rocks. What a great little addition.

It is missing one use case that I could find, and that is where a 404
occurs because a RoutingError occured at the controller level. If it
happens after the controller has been found (say a view or ID is
wrong), then this works. But if application.rb is not called, then it
goes back to the default rails code instead of through the exception
_notificaiton plugin.

This is easily fixed if two changes occur:
- you wrap the ExceptionNotification module around the ActionController
module like so:

module ActionController
  module ExceptionNotifiable

- in init.rb, add this:

require 'exception_notifiable'

that is all it takes to self register with the ActionController::Base,
which is what I think we really want.

Jamis, what do you (or anyone else for that matter) think?

Thanks again jamis for a killer plugin,
Adam