Use AssetsLibrary instead of UIImagePickerController. Thanks to @norio_nomura!
Use the same audio pitch algorithm in Player and Exporter.
Try to be active an audio track if the export session's preset is passthrough. But failed.
Merge remote-tracking branch 'norio_nomura/master' into merge_test

Conflicts:
	SlowDown/Base.lproj/Main.storyboard
	SlowDown/ViewController.m