on perl 5.21.6 and later, aliased.pm through 0.31 trigger the new warning about lexicals (RT#100359)

e.g.
http://www.cpantesters.org/cpan/report/1a6b8b8a-6dfc-11e4-80e2-78b510862755
use head2 for config options, so they show up in the table of contents
Dist-Zilla-Plugin-PromptIfStale-0.031

          - add a dynamic test prereq to avoid new warnings added to perl 5.21.6