Fix Ex 5 in the tutorial to match its expansion

The expansion of the example 5 in the tutorial, with sweet.js version 2.0.0, gives for me:

(function (bb8_5) {
  ;
  console.log(bb8_5.beep());
}(new Droid("BB-8", "orange")));

So I added one more ctx.next() and rebuild the docs. Maybe would be better also a check to see if the ; exists?