tor/changes/prop140

  o Major features (directory protocol):
    - Tor relays and authorities are now able to serve clients an
      abbreviated version of the networkstatus consensus document,
      containing only the changes since the an older consensus document that
      the client holds. Clients now request these documents when
      available. When this new protocol is in use by both client and server,
      they will use far less bandwidth (up to 94% less) to keep an up-to-date
      consensus. Implements proposal 140; closes ticket 13339. Based
      on work by by Daniel Martí.