Ember-cli-notifications not showing icons

i'm trying to use the Ember-cli-notifications in my new app, but the icon is not working at all.

Following the documentation, i need put this i n my configuration file:

  'ember-cli-notifications': {
    icons: 'bootstrap'
  }

And i already did.. but still, nothing happens and no error shows in my console or terminal.

Somethings this add-ons have poor documentation.. so, anyone who understand embers better them i do.. could answer me if i'm missing something?

Thanks.