google cloud integration
add firewall to google default network for given project

- to ensure that pe ports are open
added retry for network failure errors
split out google compute related code to its own class

- tidy!
added yard documentation to google compute code + new platform class

- we like docs!
- i should do this more often!
- please don't check for grammar
Merge pull request #167 from anodelman/google-cloud

Google cloud support in beaker