v0.2.1

Fix

• Get non-empty objects from ZoteroItem (so that we have a JSON serializable object) (6b79fc9)
• Ignore highlights more than 8191 characters (readwise limit for a highlight.) (7503324)

Documentation

• Improve printouts for both Zotero and Readwise operations (5a22717)
• Define Zotero2ReadwiseError exception object. (7d5022a)