Support --exclude-pattern

PHP-Analyzer has undocumented features that allow an '--exclude-path` command line value, as well as `--include-pattern` and `--filter-pattern`. See https://github.com/scrutinizer-ci/php-analyzer/blob/master/src/Scrutinizer/PhpAnalyzer/Command/RunCommand.php#L42

This PR just considers the exclude, as that's all I needed.

There's probably a neater way of doing my code, but as this is my first contribution to anything Grunt-related, I just went with what works!