Merge upstream master into the IFAD branch

* master:
  Jruby is not working. I would like to add this support. Until we fix it moving to allow_failures
  Remove ree support. Let's support only MRI and JRuby. I would like to remove 1.8.x support soon.
  Fix debugger development dependency
  Add travis ci
  Change the way we are running the specs. This way is more common.
  Adding JSON oj support, for max performance parsing JSON
  Upgrading kaminari development dependency version
  follow Kaminari 0.14.0 API change: num_pages  =>  total_pages
  bumping version
  Completed support for :allow_blank property option and enabled support to ignore blank values in associations. This is especially useful for html forms that provide empty values
  Finalizing changes for Rails 3.2 support, which is still backwards compatible with 3.0
  Removing old code, working on ActiveModel support
  Added :allow_blank option to properties
  Use couchrest 1.1.3
  Depending on any recent version of Rails
  Implements to_sym for property objects ( should have along with to_s, since this is a war that will never end )
  Class typecast method available for special properties