Update Time-Piece to CPAN version 1.23

  [DELTA]

  1.23      2013-09-06
        - add a LICENSE file (thanks, John Peacock!)
        - make sure Time::Seconds loads Exporter, which it relies on (thanks,
          GFUJI and TOKUHIROM!)
        - fix day of year parsing (like "%y%j") (thanks, Doug Wilson)