Option like --check? #35

As part of my build, I would like to check to make sure that the modules match my packages.json, but my build cannot have network dependencies so npm install will not work. shrinkwrap can do this but as far as I can tell there is not flag like --check to have it just run the check and nothing else. Would you consider adding something like this? Or is there an existing method that I can use?

Thanks!