Handle versions of Figshare and other pre-print repositories

[jgrethe]

Figshare, for example, supports versioning of a pre-print with new versions (each with a citation to the dataset).

• doi:10.6084/m9.figshare.23624622
• doi:10.6084/m9.figshare.23624622.v2
• doi:10.6084/m9.figshare.23624622.v3

Will need to handle this. Probably want to:

1. grab the latest version as primary citation
2. fold other versions into primary citation