Properly declare the release script's deps

Previously we made the assumption that `mixlib-shellout` is installed
on any machine that would execute the release script.
Add supporting JSON for releasing ChefDK

These files are used by `jenkins/release.rb` when releasing builds to
Omnitruck’s S3 buckets.
Merge pull request #144 from opscode/schisamo/chefdk-omnitruck

Release ChefDK packages to Omnitruck's S3 buckets