testing a new method to run the tests / removed last traces of bogus constants

It's practically impossible to create a proper 5.2-compatible setup of packages
for PHPUnit. Even falling bck to 3.5 results in internal PHPUnit errors.

Let's try to use the system-wide PHPUnit always on Travis. Developers can
choose to use the local PHPUnit, if they want to. We continue to install with
--dev in case we really have a library that we need locally to test Sally.
do not load our own autoloader (and try to overwrite global functions) when running in PHPUnit