`destroy` should prompt for confirmation.

[brandonkelly]

Currently running nitro destroy immediately permanently destroys the machine. It should prompt for confirmation first.

$ nitro destroy
Are you sure you want to permanently destroy your nitro-dev machine? [n] $ y
Permanently removed nitro-dev

(While you’re in there, “removed” should be changed to “destroyed” in that last message.)

[angrybrad]

Resovled in 274b94e