Refactor msi building logic into omnibus-ruby as a packager

This PR goes along with: https://github.com/opscode/omnibus-ruby/pull/149 & https://github.com/opscode/omnibus-software/pull/186

Investigating some [CI failures](http://ci.opscode.us/view/Chef%20Client%20Build%20Pipeline/job/chef-client-test/784/) but would like to get some input on seeing if I've missed anything.