* By adding Coding Standard to calls, phpcs will not lookup the standard
to use in our phpcs.xml.dist, which is used to check the project
itself.
* Instead it will use the provided standard.
* Allows running all further sniffs, even if a single sniff fails.
* Shows all issues at once in output.
* Use native SplFileInfo instead of Symfony, as we have no need for the
dependency.
Relates: #46
* Allow phpcbf / diff to be optional, as not all tests are fixable.
* Provide more information in case of error.
* Provide phpunit dist to run phpunit without anything special.
Relates: #46
