Add dummy tasks folder to prevent 'load-grunt-tasks' from logging an error

- 'load-grunt-tasks' by default tries to `grunt.loadNpmTasks` for every
  dependency named /grunt-*/.
- By adding a tasks directory with a js file that doesn't actually load
  any grunt tasks, we prevent 'load-grunt-tasks' from logging an error
  saying it can't find our module.
Tweaks README again