Log Message:
p5-Tree-DAG_Node: update to 1.31.

1.31  2018-02-14T09:08:00
	- Clarify licence issue by changing the reference in the DAG_Node.pm file from \ 
Artistic V 2
		to Perl, so it now matches what I preemptively put in Makefile.PL and the \ 
LICENSE file.
		Sean Burke has kindly agreed to this change.
		$thanx x $many to Gregor Herrmann (Debian Perl Group) for reporting this via \ 
github.