0.3.0

• Adds support for Python 3.10.
• Improves download-files command to resume interrupted downloads when
  using HTTP downloads with pycurl engine.
• Improves XRootD downloader by using vanilla XRootD package. Changes
  xrootdpyfs to xrootd download engine.
• Improves download-files command with a new option --download-engine
  to select pycurl or requests engines when downloading files over
  HTTP.
• Fixes minor issues with file index unwinding and output directory handling.