Ar-code attachment_fu

parent_options[:processor] is used to determine whether to load the processor, to stop child classes re-loading (or loading a different) processor. But this doesn't work for children of child classes.

Example:

class Attachment < ActiveRecord::Base
  has_attachment :processor => :mini_magick
end

class Child < Attachment 
  # is fine
end

class Grandchild < Child 
  # parent_options[:processor] is nil, so the default 
  # processor is loaded, which makes for big-time crazyness
end

This commit fixes the problem: http://github.com/ianwhite/attachment_fu/tree/fd43d97