Make png file names more regular

go/archive/archive.go

		exit("rand.Read", err)
	}
	cmd := exec.Command("prince", "--javascript", "--raster-output", fmt.Sprintf(".archive/%x-%%d.png", buf), u.String())
	cmd := exec.Command("prince", "--javascript", "--raster-output", fmt.Sprintf(".archive/%x-%%02d.png", buf), u.String())
	cmd.Stderr = os.Stderr
	cmd.Stdout = os.Stdout
	err = cmd.Run()