Modify XML-fetching script to build zips from corpus backup
Modify XML-fetching script to build zips from corpus backup

It now builds complete zip archives, with asset files, but with an
up-to-date article XML file substituted for the one found in the corpus
backup.

PLOS/rhino,PLOS/rhino,PLOS/rhino,PLOS/rhino,PLOS/rhino