3.0 phpunit 4

Changed some tests to avoid fatal errors in PHPunit 4. We cannot start using it right away, though,  without fixing several problems:

* Anything touching the session with error out, despite using --stderr. This calls for an urgent Session rewrite
*  App::classname() cannot be tested as it is static and PHPunit removed the support for mocking statics. A solution to this would be to either make App non-static and/or remove the namespace fallbacking feature from the core. That is, you will need to be explicit when loading classes using short name:  `Cake.Auth` vs `Auth` in components,  for example