title: Callback function after image has downloaded
body: <p>I'm trying to save an image download with the <a href="https://github.com/mikeal/request">request</a> module. With this  </p>
  
  <pre><code>request('http://google.com/images/logos/ps_logo2.png').pipe(fs.createWriteStream('doodle.png')); 
  </code></pre>
  
  <p>It works fine. 
  But I want to be able to do something else after the image has been completely downloaded.
  How can provide a callback function to fs.createWriteStream ?</p>