Issue with vendored_phpmd_path

[shanept]

Hi @g105b

This issue is practically identical to the php-actions/phpunit#51 issue.

The parameter vendored_phpmd_path handles the vendored path identically to how the phpunit handler currently does, resulting in the same issue. I have gone to the liberty of writing my same modifications into this project as well.

This issue is just a formality, it is solved by my pull request.

Kind regards,
Shane Thompson