Xcode Swift Add Black Outline To SKLabelNode

Question

I am trying to add a black border around my text like it is done in flappy bird, but I can not figure out how to do it within swift. I am able to fill in the label, but it does not allow me to do anything with adding a border or a outline around it. Is there anything that can be done to add a black outline to this code?

                self.scoreLabel.fontName = "04b_19"
                self.scoreLabel.text = "\(self.score)"
                self.scoreLabel.fontSize = 80
                self.scoreLabel.position = CGPointMake(CGRectGetMidX(self.frame), CGRectGetMidY(self.frame) * 1.58)
                self.scoreLabel.fontColor = SKColor.whiteColor()
                self.scoreLabel.zPosition = 6
                self.addChild(self.scoreLabel)