PHPunit 4 compatibility

fixes #331

Check if PHPUnit version is under 4.0.0

https://github.com/sebastianbergmann/phpunit/wiki/Release-Announcement-for-PHPUnit-4.0.0#obtaining-phpunit-40

> Please note that starting with PHPUnit 4.0.0 the PEAR package of PHPUnit is merely a distribution mechanism for the PHP Archive (PHAR) and that many of PHPUnit's dependencies will no longer be released individually via PEAR. We will eventually stop making releases of PHPUnit available via PEAR altogether.