Segment words according to their morphemes.

def morphemes(args):
  """Segment words according to their morphemes."""
  morfessor = load_morfessor_model(lang=args.lang)
  for l in args.input:
    words = l.strip().split()
    morphemes = [(w, u"_".join(morfessor.viterbi_segment(w)[0])) for w in words]
    line_annotations = [u"{:<16}{:<5}".format(w,p) for w, p in morphemes]
    _print(u"\n".join(line_annotations))
    _print(u"")