title: What's the callback for retrievePeripheralsWithIdentifiers:'s in iOS7
body: <p>The central manager selector <code>retrievePeripheralsWithIdentifiers:</code> replaces <code>retrievePeripheral:</code> in iOS 7.</p>
  
  <p>But what callback method (central manager delegate selector) replaces <code>centralManager:didRetrievePeripherals:</code>?</p>
  
  <p><code>centralManager:didRetrievePeripheralsWithIdentifiers:</code> doesn't seem to exist.</p>