add missing load of Data::Dumper

I'm not sure exactly how this is an issue when it has never been before, but I encountered

    Can't locate object method "new" via package "Data::Dumper" at /Users/ether/.perlbrew/libs/16.3@std/lib/perl5/Dist/Zilla/Plugin/MakeMaker/Awesome.pm line 134.

...while attempting to build Moose using Test::Builder 1.5 alpha.