Display cakebox hostname instead of ip-address in post-up-message

[bravo-kernel]

It would be charming if the vagrant post-up-message would show the user specified hostname instead of the ip-address. Could be done by e.g. checking if the host is ping'able during vagrant up.

==> default: Your box is ready and waiting.
==> default:
==> default: => Login to your Dashboard by browsing to http://pingable-hostname
==> default: => Login to your virtual machine by running: vagrant ssh