make had-no-warnings tests author only, to avoid surprise failures when upstream things change

e.g.
http://www.cpantesters.org/cpan/report/b8f4f612-6cc9-11e4-927e-bb522fe5cfa2
remove prereqs that are only used if Moose < 2.1300
MooseX-Role-WithOverloading-0.16

          - fix tests that failed due to an interaction between aliased.pm and
            perl 5.21.6