* 0.2
    * Added 'cleanuprs' management command and config option
      'HASH_KEYS_CHECK_FOR_EXPIRY' to clean up session data
      in hash mode.
    * backward incompatibility: hash mode now stores expiry date in 
      big-endian order for simpler comparation, still 4 bytes.
      Please cleanup session if you're using hash mode in 0.1.
* 0.1
    * Initial version.
