title: Setup a callback after a transaction has committed
body: <p>I'm trying to achieve something that I guess has a simple answer but somehow I can't find it reading the source code of <code>ember-data</code>.</p>
  
  <p>I would like to trigger an action after a particular set of modifications have been committed to the datastore. This my current code:</p>
  
  <pre><code>var transaction = App.store.transaction();
  user = App.get('currentUser');
  transaction.add(user);
  user.set('name', "Michael Jackson");
  transaction.commit();
  App.navigate('dashboard');
  </code></pre>
  
  <p>My first attempt was to add an observer over this user's <code>isDirty</code> property, but a) it doesn't seem idiomatic and more importantly b) I would have to remove manually that observer at the end - that's prone to errors if some exception raises in between and doesn't get removed, for instance.</p>
  
  <p>Any ideas? How would you do this?</p>