Support latest phpunit versions
Currently we extend a class in our unit tests that belongs with a pre-namespaced phpunit. There is a migration path summed up as
"If you want to update a simple project, where the only usage of PHPUnit classes is to create tests, you are very lucky. You need to require at minimum PHPUnit 4.8.35 or 5.4.3, which includes the FC class PHPUnit\Framework\TestCase as an alias for \PHPUnit_Framework_TestCase."
But from my digging I think we need to remove dbunit first (sebastianbergmann/dbunit#217) - which I've started doing