Ember helpers - how to include "Handlebars" lib

Ember CLI
1

I’ve created a new app by

ember new my-app

The helper file my-app\app\helpers\highlight.js

import Ember from 'ember';

export default Ember.Handlebars.helper('highlight', function(value , options) {
    var escaped = Handlebars.Utils.escapeExpression(value);
    return new Ember.Handlebars.SafeString('<span class="highlight">' + escaped + '</span>');
});

/*export default Ember.Handlebars.makeBoundHelper(function(value, options) {
    var escaped = Handlebars.Utils.escapeExpression(value);
    return new Ember.Handlebars.SafeString('<span class="highlight">' + escaped + '</span>');
});*/

is used like

my-app\app\templates\about.hbs

<h1>About</h1>

{{highlight 'About'}}

Without the commented out line in my-app\app\index.html

...
{{content-for 'body'}}

<!--<script type="text/javascript" src="http://cloud.github.com/downloads/wycats/handlebars.js/handlebars-1.0.0.beta.6.js"></script>-->
<script src="assets/vendor.js"></script>
<script src="assets/my-app.js"></script>
...

the console reports:

file changed helpers\highlight.js

helpers/highlight.js: line 4, col 19, 'Handlebars' is not defined.

I tried even (my-app\config\environment.js):

EmberENV: {
  FEATURES: {
      'ember-handlebars': true

The error message was the same. Please, could you help to properly add the helper method to my test app.

====================================== UPDATE

Fixed:

ember\my-app\bower.json

    ...
    "qunit": "~1.17.1",
    "ember-handlebars": "http://cloud.github.com/downloads/wycats/handlebars.js/handlebars-1.0.0.beta.6.js"
  }

bower install

...
// var escaped = Handlebars.Utils.escapeExpression(value);
var escaped = Ember.Handlebars.Utils.escapeExpression(value);
...