Get authors from git commit history

[johrstrom]

It may be nice to append authors from the git history. Maybe even the commits since the last tag. I know I'd appreciate it just to have the list of committers for attribution.

[vsoch]

This feels like it's going into tributors territory - perhaps it makes sense to use tributors to generate the zenodo.json (and likely I'd need to update it to enable that) and then use here? Or if it's simple enough we could add a similar function here to just look for new authors.