Use generated ssh key as user ssh key

I think it would be useful if the ssh key generated was used not only for login but as the SSH key for the Vagrant VM as well. Users could then easily register this as their SSH key in Github or w/e other services they are using for use with ssh checkouts. It would save the user a step of having to generated a key themselves once they've provisioned the VM.

If this isn't a viable solution, then perhaps generating a second/third pair of SSH keys (one pair for root and vagrant or one pair each) and save these keys to a secondary folder, like `./puphpet/files/dot/ssh/root` and `./puphpet/files/dot/ssh/vagrant`