title: How to set serviceUnavailableAlertEnabled in RestKit v0.20.0
body: <p>In Restkit versions before v0.20.0 it used to be a simple enough to check for service unavailability and show appropriate responses. </p>
  
  <pre><code>objectManager.client.serviceUnavailableAlertEnabled = YES;
  </code></pre>
  
  <p>How can we achieve the same in latest RestKit?</p>