CITATION.cff and README recommend citing differently

[ajwheeler]

Just flagging that CITATION.cff is out of sync with the citation recommendation in the README. I'm assuming you prefer we cite the paper on the arxiv?

Btw, thanks for the nice package.

[ChrisRackauckas]

Yes we should update that.

[avik-pal]

Thanks for pointing it out. I have updated it!