def extend_trailing_preposition(max_words,words)
    while words.length < max_words && words[-1] && words[-1][PREPOSITION_REGEX]
      words << model.next_word(words[-1],randomizer)
    end
    words
  end
def extend_trailing_preposition(max_words,words)
    while words.length < max_words && words[-1] && words[-1][PREPOSITION_REGEX]
      words << model.next_word(words[-1],randomizer)
    end
    words
  end
Check to see if the sentence ends in a PREPOSITION_REGEX word.
 If so, add more words up to max-words until it does.