dendro v0.3.2

Fixed

• Archive::vacuum_into works on the read handle. Archive::open sets
  query_only, and SQLite refused VACUUM INTO under it ("attempt to write
  a readonly database") although the statement writes only the
  destination, so a live archive, which allows a second party no other
  handle, could not be dumped this way. query_only is lifted for the one
  statement and restored on every path; the connection is still
  SQLITE_OPEN_READ_ONLY, so the archive stays unwritable.