title: Animate CALayer border change
body: <p>I'm setting a <strong>border</strong> width and color to a <code>UIView</code> subclass this way:</p>
  
  <pre><code>- (void) setViewBorder
  {
      self.layer.borderColor = [UIColor greenColor].CGColor;
      self.layer.borderWidth = 3.0f;
  }
  </code></pre>
  
  <p><strong>My question is:</strong> How can I animate this? Thanks.</p>