For anyone else finding this now, like me, it's changed:

  /** Broadcast a vote */
  steem.broadcast.vote(
    postingWif,
    username, // Voter
    'firepower', // Author
    'steemit-veni-vidi-vici-steemfest-2016-together-we-made-it-happen-thank-you-steemians', // Permlink
    10000, // Weight (10000 = 100%)
    function(err, result) {
      console.log(err, result);
    }
  );