Switch from containers/image to go-containerregistry (#140)

* Vendor changes for go-containerregistry switch.

* Manual changes for go-containerregistry switch.

The biggest change is refactoring the tarball unpacking.

* Pull more of container-diff out.

* More vendor removals.

* More unit tests.

vendor/github.com/docker/distribution/reference/helpers.go

@@ -1,42 +0,0 @@
-package reference
-
-import "path"
-
-// IsNameOnly returns true if reference only contains a repo name.
-func IsNameOnly(ref Named) bool {
-	if _, ok := ref.(NamedTagged); ok {
-		return false
-	}
-	if _, ok := ref.(Canonical); ok {
-		return false
-	}
-	return true
-}
-
-// FamiliarName returns the familiar name string
-// for the given named, familiarizing if needed.
-func FamiliarName(ref Named) string {
-	if nn, ok := ref.(normalizedNamed); ok {
-		return nn.Familiar().Name()
-	}
-	return ref.Name()
-}
-
-// FamiliarString returns the familiar string representation
-// for the given reference, familiarizing if needed.
-func FamiliarString(ref Reference) string {
-	if nn, ok := ref.(normalizedNamed); ok {
-		return nn.Familiar().String()
-	}
-	return ref.String()
-}
-
-// FamiliarMatch reports whether ref matches the specified pattern.
-// See https://godoc.org/path#Match for supported patterns.
-func FamiliarMatch(pattern string, ref Reference) (bool, error) {
-	matched, err := path.Match(pattern, FamiliarString(ref))
-	if namedRef, isNamed := ref.(Named); isNamed && !matched {
-		matched, _ = path.Match(pattern, FamiliarName(namedRef))
-	}
-	return matched, err
-}