Build: rename the config files (#49)

Both PHPUnit as well as PHPCS offer the possibility to use a `.dist` file for project configurations.
Using that, will allow individual developers to overrule the project file with their own configuration which may, for instance, contain environment variables local to their system.

Author: jrfnl

.gitignore

@@ -1,2 +1,5 @@
 /composer.lock
 /vendor/
+phpunit.xml
+.phpcs.xml
+phpcs.xml