Ability to specify icon classes

[adamlc]

It will be great to be able to specify the classes for icons. We use semantic-ui. I see you can specify an "icons" variable, maybe we could have an iconClasses option like this?

'ember-cli-notifications': {
  iconClasses: {
    info: "glyphicon glyphicon-info-sign",
    ..... etc
  }
}

[mansona]

We no longer support changing the icon set at build time now that #251 has been released. We have simplified the CSS stack so it should be possible to override the icons using CSS 🤔 let me know if you have any questions or would like to open this issue again 👍