Updated to support GCE API v1beta16 (gcutil-1.10.0)

Bumping up to v0.2.0

Fixes #17, fixes #18; updated to support GCE public API v1beta16 via gcutil-1.10.0.
 * Now supports --service_account_scopes when creating a new instance.
 * Improved persistent disk detection and re-use

Tested on GCE Debian-7 instances running both PE3.1 and OS-provided puppet v2.7.23.