title: ember-cli 0.2.1 - generated addon test cannot find mixin
body: <p>I have recently upgraded ember-cli 0.2.0 to 0.2.1 and I ran the following command to generate a mixin:</p>
  
  <pre><code>ember g mixin listener
  </code></pre>
  
  <p>The generate file was place in <code>addon/mixins/listener.js</code>.</p>
  
  <p>The generated test looks like this:</p>
  
  <pre><code>import Ember from 'ember';
  import ListenerMixin from '../../../mixins/listener';
  import { module, test } from 'qunit';
  
  module('ListenerMixin');
  
  // Replace this with your real tests.
  test('it works', function(assert) {
    var ListenerObject = Ember.Object.extend(ListenerMixin);
    var subject = ListenerObject.create();
    assert.ok(subject);
  });
  </code></pre>
  
  <p>The test fails with the following error message:</p>
  
  <blockquote>
    <p>Could not find module <code>dummy/mixins/listener</code> imported from
    <code>dummy/tests/unit/mixins/listener-test</code></p>
  </blockquote>
  
  <p>My mixins should be in <code>/addons/</code> and not <code>/app/</code></p>
  
  <p>What do I need to change for the tests to find the module?</p>
  
  <p>When I upgraded from 0.2.0 to 0.2.1 I followed the docs for upgrading and ran all the steps in the docs</p>
  
  <p>but this line:</p>
  
  <pre><code>ember init
  </code></pre>
  
  <p>Returned this error which I assume is something to do with it:</p>
  
  <blockquote>
    <p>Generating an addon in an existing ember-cli project is not supported.</p>
  </blockquote>