improve cli's tests description and remove 'should'
improve core_ext's tests description and remove 'should'
improve formatter's tests description and remove 'should'
improve rb_support's tests description and remove 'should'
improve runtime's tests description and remove 'should'
improve wire_support's tests description and remove 'should'
improve world's tests description and remove 'should'
improve cucumber's tests description and remove 'should'