upgrade version of command

[elisarver]

command@v0.1.0 is now out, update tests to use it.

Previously the command.New accepted functional options, but the exec.Cmd rework of the package has made this more go-stdlib-like.

before:

ctx := context.TODO()
cmd := command.New(command.WithDir("somewhere"))
output, err := cmd.Run(ctx, "echo", "hello world")

after:

cmd := command.New("echo", "hello world")
cmd.Dir = "somewhere"
output, err := cmd.CombinedOutput()