addRestoreCaseException() not working

The following example provided in the docs (v1.1.0) doesn't work.

````// Example of adding a token exception whose case should not be restored:
    this.service.pluralize('promo ID') //=> 'promo IDS'
    this.service.addRestoreCaseException('IDs')
    this.service.pluralize('promo ID') //=> 'promo IDs'
````

In both cases it prints 'promo IDS'.