A lot of work that had to happen here:
* Better reuse of config
* Ability to mark VPC & InternetGateway as shared
* Find models relative to the executable, to run from a dir-per-cluster
Fixes#95
We allow --zones & --master-zones to be specified separately now, but we
validate for common errors (using a region where you meant a zone,
duplicating a zone, spanning regions, entering an invalid AZ etc)
* GCE support only
* Key and secret generation
* "Direct mode" makes API calls
* "Dry run mode" previews the changes
* Terraform output (though key generation not working for master ip)
* cloud-init output (though debian image does not ship with cloud-init)