title: How to listen for Picasso (Android) load complete events?
body: <p>Is there a way to listen for events from Picasso when using the builder like:</p>
  
  <p><code>Picasso.with(getContext()).load(url).into(imageView);</code></p>
  
  <p>I'm trying to call <code>requestLayout()</code> and <code>invalidate()</code> on the parent <code>GridView</code> so it'll resize properly but I don't know how to set a listener or callback. </p>
  
  <p>I see that Picasso has error event reporting, but is there a success event?</p>