Once the Vm has been created, us the VBox setting

there's no point ssh-ing to the default port if the vm was set up
differently.
Merge pull request #134 from SvenDowideit/use-actual-vbox-ports

Once the Vm has been created, use the VBox setting
boot2docker ip outputs the host only network IP

All the nice words are in stderr, and only the IP address goes to
stdout, so its simple to use in an ENV / script.
Merge pull request #136 from SvenDowideit/use-actual-vbox-ports

boot2docker ip outputs the host only network IP