HTTP Error 404 when trying to load data from private repo

[rmnldwg]

If I try to load data from the private repository, it fails because the package naively assembles a raw.githubusercontent.com URL string from the dataset description and passes that to pandas. This will obviously fail for a private repo.

For private repos, it needs to attempt loading via the API/PyGithub package. This might also be a safer way for the public case...