code: function(n) {
        var result = '';
        n = n || 0;
        this.codes(function(c) {
          result += chr(c + n);
        });
        return result;
      }
docs: *
  @method shift(<n>)
  @returns Array
  @short Shifts each character in the string <n> places in the character map.
  @example
  
  'a'.shift(1)  -> 'b'
  'ク'.shift(1) -> 'グ'
  
  *