Support PHPUnit 9.x

[JeroenDeDauw]

No description provided.

[coveralls]

Coverage increased (+0.2%) to 99.18% when pulling b12a5ae on JeroenDeDauw:patch-1 into 90cce5d on oradwell:master.

[JeroenDeDauw]

Hah not this easy

OckCyp\CoversValidator\Tests\Command\ValidateCommandTest::testPrintsConfigFileUsed

Error: Class 'PHPUnit\Util\Configuration' not found

/home/travis/build/oradwell/covers-validator/src/Loader/ConfigLoader.php:17

/home/travis/build/oradwell/covers-validator/src/Handler/InputHandler.php:23

/home/travis/build/oradwell/covers-validator/src/Command/ValidateCommand.php:52

/home/travis/build/oradwell/covers-validator/vendor/symfony/console/Command/Command.php:255

/home/travis/build/oradwell/covers-validator/vendor/symfony/console/Tester/CommandTester.php:76

/home/travis/build/oradwell/covers-validator/tests/Command/ValidateCommandTest.php:37

https://travis-ci.org/github/oradwell/covers-validator/jobs/663728817

[oradwell]

@JeroenDeDauw thanks for opening this PR. sorry I've completely missed this. I'll take a look this week

[oradwell]

@JeroenDeDauw I've done some work on this last night. it seems harder than I imagined. they've completely changed Configuration classes. I'm having trouble obtaining the list of tests

See here: https://github.com/oradwell/covers-validator/tree/phpunit-9-compatibility

[JeroenDeDauw]

🎉

You did all the work, no need to credit me!

[oradwell]

@JeroenDeDauw you created the PR and changed composer.json. I think that's enough for getting some credit. I didn't even know PHPUnit 9 was released