I don't know about the rest of your citation format, but I think citing me as the primary author is fine. There have been a number of other contributors but I don't think it'd make sense to list them all or to select a couple. Perhaps you can indicate somehow that additional contributors can be found in the CONTRIBUTORS.txt file?
For the URL, I always point to github and not to read the docs. You can do what ever you think is best for your readers though.
Good luck with the paper :)