privacy-friendly helper to refresh a GnuPG keyring

 parcimonie is a daemon that slowly refreshes a GnuPG public keyring
 from a keyserver.
 .
 Its refreshes one key at a time; between every key update parcimonie:
   - sleeps a mostly random amount of time
   - asks Tor to change circuits.
 .
 This process is meant to make it hard for an attacker to correlate the
 multiple performed key update operations.
 .
 See the included design document to learn more about the threat and
 risk models parcimonie attempts to help coping with.