GKLeaderboardViewControllerDelegate has been suppl...

GKLeaderboardViewControllerDelegate has been supplanted by the more general GKGameCenterControllerDelegate, which includes support for Achievements and Challenges as well as Leaderboards.
To summarize:
// the following are DEPRECATED as of iOS 7.0:
// GKLeaderboardViewController [DEPRECATED as of iOS 7.0]
// GKLeaderboardViewControllerDelegate [DEPRECATED as of iOS 7.0], with its one required method: leaderboardViewControllerDidFinish(_:) [DEPRECATED as of iOS 7.0].
// the following are NOT deprecated and should be used in lieu of the above.
// GKGameCenterViewController [introduced in iOS 6.0]
// GKGameCenterControllerDelegate [introduced in iOS 6.0], with its one required method: gameCenterViewControllerDidFinish(_:) [introduced in iOS 6.0].