more diagnostics on failure
ensure no trailing whitespace was added to Makefile.PL
fix inaccurate test description
look for more variants of the "use" line
also test the main header
strip ExtUtils::MakeMaker (and friends) from configure requires
Dist-Zilla-Plugin-MakeMaker-Fallback-0.015

          - remove configure requires declarations added for Makefile.PL
            (technically they are only needed when configure requires is
            already not being respected)