temporary solution to https://github.com/datamapper/dm-types/issues/26

dm-taint.rb

# modified from https://gist.github.com/763374
module DataMapper
  module Resource
    def taint! property
      self.persistence_state = PersistenceState::Dirty.new(self) \
        unless self.persistence_state.kind_of?(PersistenceState::Dirty)
      self.persistence_state.original_attributes[properties[property]] = Object.new
    end
  end
end