Improve Travis CI configuration a bit and add PHP7.2 to the test matrix. Add PHPUnit Testdox output and optionally deploy test results on release tags. Add a configuration file for infection (Mutation Testing Framework).
Update requirements to PHP7 for dev. Add php-mock-phpunit to mock and stub global functions in a better way.
Testing several Travis CI features. Add DBs to travis execution matrix. Doxygen API docu generation and deployment to gh-pages. Update phpunit to 5.7.