Signed-off-by: Derek McGowan <derek@mcgstyle.net> (github: dmcgowan)
LayerManipulator, SnapshotManipulator -> SnapshotManager Signed-off-by: Akihiro Suda <suda.akihiro@lab.ntt.co.jp>
Signed-off-by: Stephen J Day <stephen.day@docker.com>