Integration tests

The pull request adds a basic integration test (*nix architecture only).

Features:
* define fixture paths (directory trees)
* run pdc binary against fixture
* test for `unused`, `not found` or `no namespace` messages

It should be easy to split the sample project or add new trees and tests.

What I did not expect is the total fail on this very simple example of psr-0 code.
Beside its quirks PDC did an acceptable job on some real life projects.

For consideration as development tool PDC should at least learn to cover those essentials. Most important Interface, namespaces with characters besides A-Z and proper namespace resolution.

It would definitely help the project to add further use cases that do cover the full feature set and approach real world code (especially Zend Framework 2 and Symfony level projects, as those would profit the most from PDC).