Ensure from figshare

[cthoyt]

This repo does some analysis, but wasn't able to post their data on github (https://github.com/ky66/ROBIN#data). The data is on figshare at https://figshare.com/ndownloader/files/36477873, seemingly this could be a simple wrapper around ensure() that just formats in the file number

To make this useful and worth doing, it would have to introspect some way to figure out the filename (or at minimum, the extension) before making the download and assign it appropriately. The problem is that there's no way to get it from the URL itself, so there would have to be a different caching mechanism