Update p5-Tree-DAG_Node to 1.16:

1.16  Mon Sep  9 09;26:00 2013
- Accept a patch (slightly modified by me) from Tom Molesworth
  (see RT#88501):
  - Remove 'use open qw(:std :utf8);' because of its global effect.
  - Replace Perl6::Slurp with File::Slurp, using the latter's binmode
    option for the encoding.
  - Fix docs where I'd erroneously said File::Slurp didn't support utf8.

1.15  Fri Sep  6 11:10:00 2013
- Replace Path::Tiny with File::Spec, because the former's list of
  dependencies is soooo long :-(.
  - Changed files: t/read.tree.t, Build.PL and Makefile.PL.
    See: RT#88435 for an explanation.
- Move t/pod.t to xt/author/pod.t.

(prlw1)