Reads words from a file.

def _read_words(filename):
  """Reads words from a file."""
  with tf.gfile.GFile(filename, "r") as f:
    if sys.version_info[0] >= 3:
      return f.read().replace("\n", " %s " % EOS).split()
    else:
      return f.read().decode("utf-8").replace("\n", " %s " % EOS).split()