Add fix for BSD stat

[tadukurow]

Current implementation assumes GNU coreutils version of stat, which fails on BSD. Try BSD format if GNU coreutils version fails.

fixes #501

[chef-supermarket]

Hi. I am an automated pull request bot named Curry. There are commits in this pull request whose authors are not yet authorized to contribute to Chef Software, Inc. projects or are using a non-GitHub verified email address. To become authorized to contribute, you will need to sign the Contributor License Agreement (CLA) as an individual or on behalf of your company. You can read more on Chef's blog.

Non-GitHub Verified Committers

There are 1 commit author(s) whose commits are authored by a non-GitHub verified email address. Chef will have to manually verify that they are authorized to contribute.

Please sign the CLA here.

[tadukurow]

I've verified the commit author as being me with github