New command for getting the IP address.

[zkanda]

Hi in boot2docker there's an easy command on getting the IP address of the virtualmachine, I think it would be helpful to add it here:

dinghy ip

[codekitchen]

agreed -- right now the IP is actually hard-coded and static, but that eventually needs to change since it could conflict with another virtual interface already on the user's computer.

I added a dinghy ip command in 679d314 that just returns the static IP for now.