iOS QuickLook closed callback

[spaceagegroop]

It would be nice if we can get a callback on iOS for when QuickLook is closed. I believe the following method is relevant. Any way we can get this exposed?
https://developer.apple.com/library/ios/documentation/NetworkingInternet/Reference/QLPreviewControllerDelegate_Protocol/index.html#//apple_ref/occ/intfm/QLPreviewControllerDelegate/previewControllerDidDismiss:

[enstain]

This PR #26 is going to cover this issue