How II

• If you have admin privileges (YMMV):

  RAILS_ROOT = `which rails | cut -d / -f 1-3`
  RAILS_ROOT = $RAILS_ROOT/lib/ruby/gems/1.8/gems/
  cp attr_accessor_with_default $RAILS_ROOT/activesupport-version/lib/active_support/core_ext/module/  

• If not :

  cp attr_accessor_with_defaults railsApp/vendor/plugins/activeresource/lib/active_resource/
  add a line to activeresource/lib/active_resource.rb to load the file before everything else : 
  require 'active_resource/attr_accessor_with_default'

• Or set up edge rails. . .