title: Property 'createAsync' does not exist on type 'TestBed'
body: <p>I'm using angular2-cli to create projects and this spec file is automatically made by cli for one of my component. I upgraded my app to rc4 and since then I've been encountering this issue when I run this test file. Below is the spec file:</p>
  
  <pre><code>import {
  inject, ComponentFixture, TestBed
  } from '@angular/core/testing';
  import { Component } from '@angular/core';
  import { By } from '@angular/platform-browser';
  import { MockComponent } from './mock.component';
  
  describe('Component: Mock', () =&gt; {
  let builder: TestBed;
  
  beforeEachProviders(() =&gt; [MockComponent]);
  beforeEach(inject([TestComponentBuilder], function (tcb:  TestComponentBuilder) {
  builder = tcb;
  }));
  
   it('should inject the component', inject([MockComponent],
    (component: MockComponent) =&gt; {
  expect(component).toBeTruthy();
  }));
  
  it('should create the component', inject([], () =&gt; {
  return builder.createAsync(MockComponentTestController)
    .then((fixture: ComponentFixture&lt;any&gt;) =&gt; {
      let query = fixture.debugElement.query(By.directive(MockComponent));
      expect(query).toBeTruthy();
      expect(query.componentInstance).toBeTruthy();
    });
  }));
  });
  
  @Component({
  selector: 'test',
  template: `
  &lt;test&gt;&lt;/test&gt;
  `,
  directives: [MockComponent]
  })
  class MockComponentTestController {
  }
  </code></pre>
  
  <p>The above spec file throws an error on 'createAsync', I'm pretty sure that createAsync does not exist on TestBed but I replaced TestComponentBuilder with TestBed (TestComponentBuilder has been deprecated in rc4). Please provide suggestions on how to resolve this issue.</p>