Add code sniffer functionality 

This will
* "Composer install" the PHP codeSniffer from https://github.com/squizlabs/PHP_CodeSniffer
* Add a command for our CLI application to sniff our JTracker code base using the Joomla! coding standard.

This should also be usable to run checkstyle tests on "foreign" code bases.

Test:
`tracker.php test checkstyle`