title: Access input from UIAlertController
body: <p>I've got a UIAlertController which is prompted to the user when they choose "Enter Password" on the TouchID screen. How do I recover the user's input after presenting this on screen?</p>
  
  <pre><code>let passwordPrompt = UIAlertController(title: "Enter Password", message: "You have selected to enter your passwod.", preferredStyle: UIAlertControllerStyle.Alert)
  passwordPrompt.addAction(UIAlertAction(title: "Cancel", style: UIAlertActionStyle.Default, handler: nil))
  passwordPrompt.addAction(UIAlertAction(title: "OK", style: UIAlertActionStyle.Default, handler: nil))
  
  passwordPrompt.addTextFieldWithConfigurationHandler({(textField: UITextField!) in
                          textField.placeholder = "Password"
                          textField.secureTextEntry = true
                          })
  
  presentViewController(passwordPrompt, animated: true, completion: nil)
  </code></pre>
  
  <p>I know the OK button should probably have a handler, but right now this code doesn't really do anything, but I want to display the output of the text field through a println. This is really just a test app for me to learn Swift and some new API stuff.</p>