Print IP of created droplet

[jwilk]

I'd love if pontoon droplet create printed IP of the newly created droplet.

[duggan]

For backwards compatibility, I think this might require some flags, like a --quiet to suppress the ... progress indicator and probably another option to return an arbitrary field from the Droplet's properties, but it sounds reasonable.

I'm not using Digital Ocean these days, but PRs are welcome. There's a chance I'll get around to it some rainy evening too :)