title: UITextField - shouldChangeCharactersIn with self.addSubview()
body: <p>My problem is that if I do my customization UITextField, then shouldChangeCharactersIn() method is not called, but if I do not apply to this customization, everything goes fine.</p>
  
  <p>I use the library SkyFloatingLabelTextField</p>
  
  <p>First file:</p>
  
  <pre><code>override func viewDidLoad() {
      super.viewDidLoad()
  
      emailField.setRegistrationFieldStyleWith(title: "E-mail")
      emailField.delegate = self
  }
  </code></pre>
  
  <p>Second file with Extensions:</p>
  
  <pre><code>func setRegistrationFieldStyleWith(title: String) {
      let textField = SkyFloatingLabelTextField(frame: CGRect(x: 0, y: 0, width: 215, height: 40))
      textField.placeholder = title
      textField.title = title
  
      textField.tintColor = overcastBlueColor 
      ...
      ...
  
      self.addSubview(textField)
  }
  </code></pre>
  
  <p>Maybe who faced with this library? Or input processing method starts to behave differently, if the fields to customize?</p>