function handleYearChange() {
  if (range.from && range.to) {
    query.bind([range.from, range.to]).exec().then(function() {
      $('#num_movies').text(model.count.toString());
    });
  }
}
The parameter to query. UI will change the values. It will be observed by
the data layer and update the model above. So the two-way circular data
binding is:

    +-> model -> UI -> range -> Data Layer -+
    +---------------------------------------+

@type {{from: number, to: number}}