`gdfstool auth_get_url` is invalid now, it's now `gdfstool auth --url`

[Masterxilo]

Either modify the README.md or add this back in.

Just curious: Why break this API? Any API is arbitrary anyways, but at least it should stay the same once out-in-the wild don't you think so?

[dsoprea]

Not sure what you're referring to. It's still perfectly valid.