title: Swift NSUserNotification doesn't show while app is active
body: <p>I am new to OSX development and I am making an app which fires a notification when something happens. But it isn't showing the notification when the app is the key app, as it is the default behavior. I want to show them even when the app IS the key app. 
  However I only found solutions to this matter that were written in objective-c  but right now I am working with Swift. I was wondering how I could I implement it with Swift.</p>