Child extractors are now directly constructed with Extractor.from_url()
if the extractor class is known beforehand, instead of using
extractor.find() and searching through all possible extractor classes.
HTML structure for gallery pages changed quite a bit, so it is now using
the embedded JSON data. This changes a lot of metadata field names, but
'gallery_id', 'title', and 'user' are still provided for backwards
compatibility.
The internal API endpoint for user galleries also changed its data
structure, but nothing too major.
Mike Fährmann