title: TypeScript and chai-as-promsied: eventually is an invalid property
body: <p>I am trying to write my Cucumber tests using TypScript, like this:</p>
  
  <pre><code>import { browser, $$ } from 'protractor';
  import { Given, Then } from 'cucumber'
  import { expect } from 'chai';
  
  Given('I navigate to the homepage', function (callback) {
    browser.get('http://localhost:4200');
    callback();
  });
  
  Then('I want to see the welcome message {string}', function (message, callback) {
    expect($$('h1').first().getText()).to.eventually.equal(message).and.notify(callback);
  });
  </code></pre>
  
  <p>However, Protractor complains:</p>
  
  <blockquote>
    <p>Error: Invalid Chai property: eventually</p>
  </blockquote>
  
  <p>How can I import this? I have tried:</p>
  
  <pre><code>import { eventual } from 'chai-as-promised';
  </code></pre>
  
  <p>but this doesn't work. How can I accomplish this? I have also tried rewriting the <code>Then</code> call using <code>await</code>, but the compiler complains that you cannot mix callbacks with async functions. Aargh!</p>