Del Todo::Task

    * I'll keep the gem ligthweight and not overload
      the Tasks (items) with new stuff as planned,
      therefore I deleted the Task class again
Add controller, Del Store and no longer used specs

    Simplified the cli.rb. Instead of having to much code in
    the run methods to care about, I moved them to the controller.rb
    and call them from the cli.rb directly
Add improvements to the controller, changed rspec to version 3
Add spec for the controller
Add the use of '.todo.yml' as file, directly in the project dir

    Instead of using the file 'list.yml' in the '.todo' directory, we changed
        (projectdir/.todo/list.yml)
        to
        (projectdir/.todo.yml)
    It should be enough to have a hidden file, IMHO no hidden directory needed