Nice clean readme, but a few things are missing:

1. Build instructions. I couldn't actually figure out how to build this without editing the Rakefile (more below). Admittedly this is missing from some of the other plug-ins, but in general it's a best practice that will save us time when new contributors get involved.
2. Example command lines: we should provide examples of life-like command-lines, i.e. not 'knife google instance create NAME -I image' but something where NAME and image are replaced with something well-formed that could actually be supplied in a real world case.
3. Some information on what is needed for knife-setup (see below)