CC-44: Add chef-dk in Chef DK omnibus packages

This PR goes along with: 

* https://github.com/opscode/chef-dk/pull/6
* https://github.com/opscode/omnibus-software/pull/134

Before merge the last commit will be fixed to point to master again. 

Tested in CI: http://manhattan.ci.opscode.us/job/chefdk-build/13/