Doc: Resizing Boot2Docker Volume with VirtualBox

The Boot2Docker VM ships with a 20G VMDK volume, which can quickly fill up if one is using large images/large numbers of images. This is a step-by-step guide for increasing the B2D volume using VirtualBox and GParted.
Our convention is to use "you" for the user and "we" for Docker, Inc. So this should be either, "We recommend you use GParted" or "You should use GParted" or some such.