Prepare for submission to JOSS

paper.md

[x] A list of the authors of the software and their affiliations
[x] A summary describing the high-level functionality and purpose of the software for a diverse, non-specialist audience
[x] A clear statement of need that illustrates the purpose of the software
[x] A list of key references including a link to the software archive
[x] Mentions (if applicable) of any ongoing research projects using the software or recent scholarly publications enabled by it