New Twiddle

application.controller.js

import Ember from 'ember';

export default Ember.Controller.extend({
  sections: [1,2,3,4,5],
  currentSection: 0,
  isLastSection: Ember.computed('currentSection', function() {
    return this.get('currentSection') === this.get('sections.length') - 1;
  }),
  sectionClassName: Ember.computed('currentSection', function() {
    return 'section-' + this.get('currentSection');
  }),
  actions: {
    gotoNext() {
      this.incrementProperty('currentSection');
    },
    gotoSection(section) {
      var sectionIndex = this.get('sections').indexOf(section);
      
      this.set('currentSection', sectionIndex);
    }
  }
});

application.template.hbs

<h1>Nav demo</h1>
<p>
	{{#if isLastSection}}
  	&nbsp;
  {{else}}
    <a href="#" {{action 'gotoNext'}}>Next</a>
  {{/if}}
</p>
<ul class="sections-nav {{sectionClassName}}">
	{{#each sections as |section|}}
    <li {{action 'gotoSection' section}}></li>
  {{/each}}
  <li class="active-marker"></li>
</ul>
<br>
<br>

styles.app.css

body {
  margin: 12px 16px;
  font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif;
  font-size: 12pt;
}

.sections-nav {
  list-style: none;
  margin: 0;
  padding: 0;
  position: relative;
}

.sections-nav li {
  border-radius: 50%;
  background: #ccc;
  cursor: pointer;
  display: inline-block;
  height: 10px;
  margin: 0 5px;
  width: 10px;
}

.sections-nav li.active-marker {
  background: #999;
  position: absolute;
  left: 0;
  pointer-events: none;
  top: 5px;
  transition: left .3s ease-in-out;
}

.section-1 li.active-marker {
  left: 24px;
}

.section-2 li.active-marker {
  left: 49px;
}

.section-3 li.active-marker {
  left: 74px;
}

.section-4 li.active-marker {
  left: 99px;
}

/* etc */

twiddle.json

{
  "version": "0.4.9",
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "https://cdnjs.cloudflare.com/ajax/libs/ember.js/1.13.9/ember.js",
    "ember-data": "https://cdnjs.cloudflare.com/ajax/libs/ember-data.js/1.13.11/ember-data.js",
    "ember-template-compiler": "https://cdnjs.cloudflare.com/ajax/libs/ember.js/1.13.9/ember-template-compiler.js"
  }
}