code: func bytelenFromWords(numWords int) (length int, maybeShorter bool) {
  	// calculate the max number of complete bytes we could store in this word
  	length = 11 * numWords / 8
  	// if one less byte would also generate this length, set maybeShorter
  	if wordlenFromBytes(length-1) == numWords {
  		maybeShorter = true
  	}
  	return
  }
docs: // given this many words, we will produce this many bytes.
  // sometimes there are two possibilities.
  // if maybeShorter is true, then represents len OR len-1 bytes