added support for fetchApis command

Hi... Per the suggestion I've forked the original and am now submitting a pull request. This augments command.js with a new command: fetchproxy. Then there is a new comand-file file fetchproxy.js which handles invoking request to download the bundle in question. If (-f/--file) is not selected it will download to the current working directory and name the resulting zip "apiName.zip". Otherwise it goes wherever -f specifies and names accordingly. Org, api and revision must be specified or you'll receive an error.

Thanks,

/geir