GCE hosts driver.

This is a basic GCE hosts driver, along with an integration test.

Auth is handled through oauth. A browser window will open when creating a host that negotiates the oauth dance, and the token is cached. The client_id and client_secret currently belong to a test project I created, but they can and should be changed to something more people can access.

I'm very new to golang, so please let me know if I did anything incorrectly/unoptimally.

I also left out the files in vendor/src/code.google.com/p/google-api-go-client/ from this commit. I can add them whenever.