Github wiki Markdown dir structure is flat / not nested

[Saggre]

Correct url:
https://github.com/Saggre/phpDocumentor-markdown/wiki/AbstractProduct

Generated url (0.1.3):
https://github.com/Saggre/phpDocumentor-markdown/wiki/classes/PhpDocumentorMarkdown/Example/AbstractProduct.md

Fix: Add GitLab and GitHub targets, which generate urls accordingly.