Refactor ZFTool to use ZendDiagnostics

* [x] Set [zendframework/ZendDiagnostics](https://github.com/zendframework/ZendDiagnostics) as dependency in composer.json.
* [x] Move all tests to new repo except MVC tests.
* [x] Naming/labeling logic - make it internal to Test\Runner.
* [x] Create a compatibility layer
* [x] Understand and consume universal tests by default.
* [x] Update docs!