Use static array to confirm vendoredPackage output.

I would definitely prefer to compare output directories, but we can't
add empty directories to .git (and adding a `.gitkeep` makes it included
in the comparison results).

Once we move to funnel, this won't be an issue (it doesn't make these
empty subdirs).
Merge pull request #19 from rwjblue/confirm-vendor-package-output

Use static array to confirm vendoredPackage output.