Add an `inactiveClass` to Ember `{{link-to}}`'s

linkto-inactive-class.js

// app/initializers/linkto-inactive-class.js
import Ember from 'ember';

export function initialize() {
  
  Ember.LinkComponent.reopen({
    classNameBindings : ['inactive'],
    inactiveClass : false, // must implicitly set
    inactive : Ember.computed('active', function(){
      // Note: `activeClass` MUST return something truthy for this to work
      return ( this.get('active') ? false : this.get('inactiveClass') );
    })
  });

}

export default {
  name: 'linkto-inactive-class',
  initialize
};