title: Backbone collection.create() does not return the updated model
body: <p>To learn backbone Im creating a Twitter like app. So you know that Twitter sends a GET request to the server every N seconds to check for new tweets. If there are new tweets, it creates the hidden <em>li</em> elements and shows the button with "N new Tweets". If you click it, it shows the hidden <em>li</em> elements, showing the new tweets.
  But the behaviour is different when you add a new tweet: the tweet is visible. You don't have to click the button to see it.</p>
  
  <p>I already have made the first part, for the hidden tweets. For the part of posting a new tweet and showing it direclty, I thought it would be easy to do by creating the new model, calling collection.create() and triggering the right event, something like:</p>
  
  <pre><code>var newTweet = new Tweet();
  newTweet.set( /* set the attributes here. Some attributes are missing, because they are calculated server side */ );
  
  var created_tweet = this.collection.create( newTweet, { silent: true, wait: true } ); // I choose silent=true because the add event on my collection is in charge of adding the new hidden tweets when there are new ones on the server
  this.collection.trigger("posted_new_tweet", created_tweet);
  </code></pre>
  
  <p>Then, my collection is subscribed to the event "posted_new_tweet", so every time a user posts a new tweet, a specific method of my collection is being called.
  This approach was working fine until I got errors due to the variable created_comment passed in the trigger: it is not "complete". I mean that the model has some attributes like <em>"id"</em> or *"created_on"* that are  undefined. These attributes are calculated server side, but I thought that if I passed <strong>wait=true</strong>, it would wait and update my model with the response given by the server (when a <strong>POST</strong> request is made to the server, it returns the new created model in json)</p>
  
  <p>Shouldn't my model have the server side attributes aswell? Is it the right approach for such a thing? In case that it is not, how can I have 2 different methods to display a collection view?</p>
  
  <p>Thank you!</p>