func didLogin() {
       let storyBoard = UIStoryboard(name: "Main", bundle: nil);
       let mainViewController = storyBoard.instantiateViewControllerWithIdentifier("mainViewControllerSB") as MainViewController
        UIView.transitionWithView(
            window!,
            duration: 0.5,
            options: UIViewAnimationOptions.TransitionFlipFromRight | UIViewAnimationOptions.AllowAnimatedContent | UIViewAnimationOptions.LayoutSubviews,
            animations: {
                self.window!.rootViewController = mainViewController
            },
            completion: nil
        )
    }