Update GCE install doc for newer instructions and more clarity

Created more detailed guide for installing docker on a Google Compute Engine instance using `gcloud` and `gcutil`. Cleaned up formatting to allow for nested code blocks in a numbered list.

Docker-DCO-1.1-Signed-off-by: Tyler Bradford <tbradford@gmail.com> (github: sirclicksalot)
Merge branch 'patch-1' of https://github.com/Sirclicksalot/docker.git into patch-1