This was the "tricky" part I talked about :)

`runSequence` takes tasks and arrays of tasks, and run them one after the other, but the tasks in arrays will run async (so you could get some nasty race conditions).

Here we want "clean-test" to finish before the rest kicks off. So:

```javascript
  runSequence(
    'clean-test',
    [
      'before-tests-mocha',
      'before-tests-vendor',
      'before-tests-data',
      'before-tests-setup',
      'before-tests-unit'
    ],
    'before-tests-index',
  cb);
```