Expanding string class to work with Unicode. You'll also need gem 'unicode'.

unicode.rb

String.class_eval do
  def downcase
    Unicode::downcase(self)
  end
  def downcase!
    self.replace downcase
  end

  def upcase
    Unicode::upcase(self)
  end
  def upcase!
    self.replace upcase
  end
  def capitalize
    Unicode::capitalize(self)
  end

  def capitalize!
    self.replace capitalize
  end
end