[TASK] Run the unit tests on TravisCI

The github repository can be found at
https://github.com/typo3-ci/ext-phpunit
and the Travis jobs at
https://travis-ci.org/typo3-ci/ext-phpunit

Resolves: #49741
Change-Id: I248775fc24718022683c1b9d55cd53ab0e523f56
Merge pull request #5 from typo3-ci/feature/travis

[TASK] Run the unit tests on TravisCI