computed without dependent keys

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  i: 1,
  iEven: Ember.computed(function() {
    return this.get('i') % 2 === 0;
   }),
  actions: {
    incrementI() {
      this.incrementProperty('i');
    }
  }
});

templates.application.hbs

<h2>
  i: {{i}}
  <button {{action 'incrementI'}}>Increment</button>
</h2>
<h2>is i even? (computed): {{iEven}}</h2>

twiddle.json

{
  "version": "0.12.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.12.0",
    "ember-template-compiler": "2.12.0",
    "ember-testing": "2.12.0"
  },
  "addons": {
    "ember-data": "2.12.1"
  }
}