Update to Omnibus 4

:construction: 

Update push server project to Omnibus 4.  
- [ ] Clean build in CI.

Ready for review @opscode/release-engineers @manderson26 

Let's recommend engineers use a test-kitchen supplied by ChefDK. 

This is the wording we use in opscode-omnibus:

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__NOTE__: Test Kitchen shoud be installed external to the local Ruby bundle. Please either use ChefDK or install the latest test-kitchen from Rubygems.

```shell
$ kitchen converge ubuntu-1204
```