Update to Omnibus 4

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

All of this code is now open under Apache 2.0. Here is the header we have been using in all other projects and software definitions:

```
#
# Copyright 2012-2014 Chef Software, Inc.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
```