Add notice of no longer being maintained

[NotAFile]

This project has not been actively maintained for years, however people unaware of this are still using it. This header in the readme redirects them to the currently maintained project.

I hope you have the time to at least merge this last pull-request.

I'd recommend also adding a notice to the repo description, as well as archiving the repository to make it clear that this repository is no longer active.

[NotAFile]

@NateShoffner