We used to throw if event listener is not a function in Stack:

```js
ReactDOM.render(
  <h1 onClick={{}}>Hello World!</h1>,
  document.getElementById('container')
);
```

<img width="565" alt="screen shot 2017-08-08 at 3 41 08 pm" src="https://user-images.githubusercontent.com/810438/29077502-2646412e-7c50-11e7-8c99-3b7f6c0a2589.png">

Fiber silently ignores this.

I think we should throw. This would let us add support for objects (e.g. for passive listener configuration) if we want to in a minor rather than a major.
it('render and then updates innerHTML and preserves whitespace', () => {
      const container = document.createElement('div');
      const html = '\n  \t  <span>  \n  testContent1  \t  </span>  \n  \t';
      const elem = <div dangerouslySetInnerHTML={{__html: html}} />;
      ReactDOM.render(elem, container);
      const html2 = '\n  \t  <div>  \n  testContent2  \t  </div>  \n  \t';
      const elem2 = <div dangerouslySetInnerHTML={{__html: html2}} />;
      ReactDOM.render(elem2, container);
      expect(container.firstChild.innerHTML).toBe(html2);
    });
  });
  describe('Attributes with aliases', function() {
    it('sets aliased attributes on HTML attributes', function() {
      spyOn(console, 'error');
      var el = ReactTestUtils.renderIntoDocument(<div class="test" />);
      expect(el.className).toBe('test');
      expectDev(console.error.calls.argsFor(0)[0]).toContain(
        'Warning: Invalid DOM property `class`. Did you mean `className`?',
      );
    });
    it('sets incorrectly cased aliased attributes on HTML attributes with a warning', function() {
      spyOn(console, 'error');
      var el = ReactTestUtils.renderIntoDocument(<div cLASS="test" />);
      expect(el.className).toBe('test');
      expectDev(console.error.calls.argsFor(0)[0]).toContain(
        'Warning: Invalid DOM property `cLASS`. Did you mean `className`?',
      );
    });
    it('sets aliased attributes on SVG elements with a warning', function() {
      spyOn(console, 'error');