Update Encode to CPAN version 2.54

Update Encode to CPAN version 2.54

  [DELTA]

$Revision: 2.54 $ $Date: 2013/08/29 16:47:39 $
! Encode.xs
+ t/cow.t
  Addressed: COW breakage with _utf8_on()
  https://rt.cpan.org/Ticket/Display.html?id=88230
! Encode.pm
  Reverted the document accordingly to #11
  https://github.com/dankogai/p5-encode/pull/10
+ t/decode.t
  Unit test for decoding behavior change in #11
  https://github.com/dankogai/p5-encode/pull/12

2.53 2013/08/29 15:20:31
! Encode.pm
  Merged: Do not short-circuit decode_utf8 with utf8 flags
  https://github.com/dankogai/p5-encode/pull/11
  Merged: document decode_utf8 behaviour more precise
  https://github.com/dankogai/p5-encode/pull/10
! Makefile.PL
  Added repository cpan metadata
  https://github.com/dankogai/p5-encode/pull/9