title: Jest cannot handle the sequelize.sync() promise
body: <p>I have this test file running with Jest:</p>
  
  <pre><code>test('this works', () =&gt; {
    Promise.resolve();
  });
  
  test('this also works', (done) =&gt; {
    setTimeout(done, 100);
  });
  
  test('this does not work', () =&gt; {
    return models.sequelize.sync({force: true, logging: false});
  });
  
  test('this also does not work', (done) =&gt; {
    models.sequelize.sync({force: true, logging: false}).then(() =&gt; done());
  });
  </code></pre>
  
  <p>Something is either weird with Sequelize.js or Jest. Ideas?</p>
  
  <p>To clarify: It's not I'm getting failing tests, all 4 tests are green. The latter two will get the database reset, but the Jest process will forever hang even after all test ran. Jest will say: 4 passed, just I have to manually quit with Ctrl + C.</p>