Generator not adding the relationship to user.rb

It's something I can easily add myself, but just wanted to let you know that the generator is not adding the association properly.

I went ahead and just added the following to `user.rb` myself:

Copied from the generators:
```
has_many :invitations, class_name: 'DeviseInvitations::Invitation',
    foreign_key: :sent_by_id, dependent: :destroy
```