[FIX] Updated to match behavior of current Rails versions (3.2.13)

* added attr_accessible to deal with mass assignment defaults (since
Rails 3.2.3 -
http://weblog.rubyonrails.org/2012/3/30/ann-rails-3-2-3-has-been-released/)
* XML generated in controllers actions was replaced with JSON
* generated migration methods up and down were replaced with change.