Clean up indentation, remove whitespace
Rework test suite and dependencies

- Move from test/unit to minitest
- Add required gem not in Gemfile yet: mocha
- Remove unused gems: activesupport, ruby-debug, shoulda-matchers
- Remove superfluous gems: shoulda
Clean up gem packaging

- gemspecs don’t need separate maintenance these days
- pushing gems is as easy as “gem push”
- provide a dynamic gemspec
- quiet tests and show our pride in a clean test run!