Add snapshot walk implementations

Temporarily remove zfs and aufs until interface update

Signed-off-by: Derek McGowan <derek@mcgstyle.net>

vendor/github.com/mistifyio/go-zfs/error.go

@@ -1,18 +0,0 @@
-package zfs
-
-import (
-	"fmt"
-)
-
-// Error is an error which is returned when the `zfs` or `zpool` shell
-// commands return with a non-zero exit code.
-type Error struct {
-	Err    error
-	Debug  string
-	Stderr string
-}
-
-// Error returns the string representation of an Error.
-func (e Error) Error() string {
-	return fmt.Sprintf("%s: %q => %s", e.Err, e.Debug, e.Stderr)
-}