Error Importing Validator Class

Using version `3.8.0` of both `ember-changeset` and `ember-changeset-validations`, I'm getting an error when importing the `Validation` class for use in a class-based custom validator: `Could not find module ember-changeset-validations/validator`. I have imported the `Validator` class exactly as the docs say:

```
import Validator from 'ember-changeset-validations/validator';

export default class MyValidator extends Validator {}
```

I can't seem to find any `Validator` class within the source code and the [tests for class-based validators](https://github.com/validated-changeset/validated-changeset/pull/76/files#diff-22d221739f9dc3ffd50b561c1f3c1fb7R2176) don't seem to extend the `Validator` class as well.

Removing `extends Validator` (like in the tests) prevents the import error from appearing, however, the validations do not run.