Feature: Incorporate figshare.Figshare into ldcoolp-figshare

[astrochun]

We are currently using our forked copy of cognoma's figshare.

In LD-Cool-P this is used in the retrieve module (download_files function) and in development preserve module. Howevr, this code was not made easiy installable with pip. The simplest solution is to add it to ldcoolp-figshare so it's included.

For simplicity, this will be the Figshare class. We might consider renaming main module to curation and create a new main.