Add test for CPAN dist with missing author

[NicholasBHubbard]

This PR adds a test to cpan_spec.rb for #1937.

[wbraswell]

This test looks good to me, @jordansissel please accept this PR, thanks!

[wbraswell]

Ping @jordansissel

[jordansissel]

% bundle exec rspec spec/fpm/package/cpan_spec.rb  -e Class::Data::Inheritable
Run options: include {:full_description=>/Class::Data::Inheritable/}
.

Finished in 2.03 seconds (files took 0.1819 seconds to load)
1 example, 0 failures

Looks good.