Add phpunit functionality 

This depends on (an will probably conflicting with) #247 

This will
* "Composer install" PHPUnit from https://github.com/sebastianbergmann/phpunit
* Add a command for our CLI application to run our JTracker unit test(s).

This should also be usable to run unit tests on "foreign" code bases (not currently).

Test:
`tracker.php test phpunit`

* Add a command to run a "test suite" - currently `phpcs` and `phpunit`

Test:
`tracker.php test run`