Fixing one test:

ReleaseCheckListTest::testCheckThatConfigurationValuesAreProductionValues
Array to string conversion
/home/travis/build/piwik/piwik/tests/PHPUnit/Core/ReleaseCheckListTest.php:47
/home/travis/build/piwik/piwik/tests/PHPUnit/Core/ReleaseCheckListTest.php:33