title: Import objective-c initializer as optional
body: <p>I've got an Objective-C class whose init method may return nil. I've used a bridging header to expose this class to Swift. Unfortunately, I now have the slight problem that Swift has imported the class's initializer as non-failable.</p>
  
  <p>How can I make Swift respect the fact that the Objective-C initializer may fail?</p>