roma/roma — pull request #22 by kou (2014-10-26 08:51:13+00:00)
Title: Use test-unit gem

test/unit.rb is minitest gem wrapper until Ruby 2.1. But test/unit.rb is
test-unit gem since Ruby 2.2. This change ensure using test-unit gem.

test-unit gem uses "module" to share tests not inheriting class.
Tests in parent classes aren't executed in test-unit gem. (They are
executed in minitest gem.)