**Do you want to request a *feature* or report a *bug*?**

bug

**What is the current behavior?**

componentWillUnmount for inner instances is never called.

Here are 2 (jest) tests, the first works, not the second.

```js
import React from "react";
import renderer from "react-test-renderer";

test("top level componentWillUnmount works", () => {
  let count = 0;
  class A extends React.Component {
    componentWillUnmount() {
      count ++;
    }
    render() {
      return <div />;
    }
  }
  const inst = renderer.create(<A />);
  inst.unmount();
  expect(count).toEqual(1);
});

test("inner componentWillUnmount works", () => {
  let count = 0;
  class A extends React.Component {
    componentWillUnmount() {
      count ++;
    }
    render() {
      return <div />;
    }
  }
  const inst = renderer.create(
    <div>
      <A />
    </div>
  );
  inst.unmount();
  expect(count).toEqual(1);
});
```

**What is the expected behavior?**

The two test above should pass. All component that are unmounted should have the proper lifecycle, whatever the nesting is.

**Which versions of React, and which browser / OS are affected by this issue? Did this work in previous versions of React?**

React 15.4.0
props: {},
      children: ['moose'],
    });
  });
  it('updates types', () => {
    var renderer = ReactTestRenderer.create(<div>mouse</div>);
    expect(renderer.toJSON()).toEqual({
      type: 'div',
      props: {},
      children: ['mouse'],
    });
    renderer.update(<span>mice</span>);
    expect(renderer.toJSON()).toEqual({
      type: 'span',
      props: {},
      children: ['mice'],
    });
  });
  it('updates children', () => {
    var renderer = ReactTestRenderer.create(
      <div>
        <span key="a">A</span>
        <span key="b">B</span>
        <span key="c">C</span>
      </div>
    );
    expect(renderer.toJSON()).toEqual({
      type: 'div',
      props: {},
      children: [