Add minitest gem to fix test runtime error with ruby 2.0
Add minitest gem to fix test runtime error with ruby 2.0

    undefined method `_run_suite' for class `Test::Unit::Runner

TwilightCoders/workflow,lorefnon/workflow-orchestrator,geekq/workflow,anujgangwar/workflow,elsurudo/workflow,imlitech/workflow,meltheadorable/workflow,cosmindorobantu/workflow