New style rule - complain if a private_attr* follows the private keyword

The cop should not allow the following:

```ruby
private

private_attr_reader :assignment, :manager, :padding
```

The resolution should be to move the private_attr_reader to the top of the file, right underneath the class, e.g. https://github.com/ezcater/ezcater-delivery/pull/163/commits/d2d08b2b7ae121e082d2f015bfcbae6161652e17