Move CLI stuff into its own dir

I think having it in its own dir like this means that people can include it in their own projects as they wish. Even though the CLI does nothing currently.
Also this is referencing `"github.com/bjeanes/go-lifx/cli"` when the path is actually `"github.com/bjeanes/go-lifx/lifx"` in your commit (though I think `cli` is better)