Resolves#607
* Deleted a duplicate Gopkg.lock block for github.com/otiai10/copy to
prevent `dep ensure` from deleting it from vendor/
* Searched for breaking changes. Only found ones for
remote.Delete/List/Write/WriteIndex. Searched for those and fixed
* Noticed that NewInsecureRegistry was deprecated and replaced it
* Update go-containerregistry
Update go-containerregistry since it can now handle image names of the
format repo:tag@digest.
Should fix#535.
Thanks @ViceIce for the fix!
* update go-containerregistry again