Use MetaJSON dzil plugin
Add README.mkdn to 'allow_dirty' in [Git::Commit]
Sort input/output file lists in compare_input_output()

There's sometimes an ordering problem. We could use 'bag' compare, but sort()
means we're not bringing in a new dependency.
Add README.mkdn to 'allow_dirty' in [@Git]
Zucchini-0.0.20

 - update preferred Bugtracker to point to github
 - don't manually specify test deps in dist.ini
 - move tests from t/testlib/ to t/lib (RT#92333)
 - use MetaJSON dzil plugin
 - sort input/output file lists in Zucchini::Test::compare_input_output