title: Custom UISearchBar with UISearchController
body: <p>The documentation for <code>UISearchController</code> says that you can override <code>- searchBar</code> to provide a custom subclass of <code>UISearchBar</code> for the controller to use. The custom search bar does get used, and its own delegate methods are called correctly, but the <code>UISearchResultsUpdating</code> method no longer gets called when the search bar changes. Do I need to do a lot of wiring things up manually, or is there something I'm missing to get the controller to behave like it does with a natively supplied search bar?</p>