We should be warning if a controlled component becomes uncontrolled, or vice versa.

I thought this was fixed in https://github.com/facebook/react/issues/5821, but apparently it was either not fixed for checkbox components, or maybe I subsequently broke it in https://github.com/facebook/react/pull/7003 (or similar).  Regardless, we should fix it.

Demo of case that should warn: https://jsfiddle.net/s4742gkk/

ReactDOM.findDOMNode(instance).checked = false;
    ReactTestUtils.Simulate.change(ReactDOM.findDOMNode(instance));
    expect(link.requestChange.mock.calls.length).toBe(1);
    expect(link.requestChange.mock.calls[0][0]).toEqual(false);
  });
  it('should warn with checked and no onChange handler', function() {
    var node = document.createElement('div');
    var link = new ReactLink(true, jest.fn());
    ReactDOM.render(<input type="checkbox" checkedLink={link} />, node);
    expect(console.error.calls.count()).toBe(1);
    expect(console.error.calls.argsFor(0)[0]).toContain(
      '`checkedLink` prop on `input` is deprecated; set `value` and `onChange` instead.'
    );
    ReactTestUtils.renderIntoDocument(
      <input
        type="checkbox"
        checked="false"
        onChange={jest.fn()}
      />
    );
    expect(console.error.calls.count()).toBe(1);
    ReactTestUtils.renderIntoDocument(
      <input type="checkbox" checked="false" readOnly={true} />
    );
    expect(console.error.calls.count()).toBe(1);
    ReactTestUtils.renderIntoDocument(<input type="checkbox" checked="false" />);
    expect(console.error.calls.count()).toBe(2);
  });
  it('should warn with checked and no onChange handler with readOnly specified', function() {
    ReactTestUtils.renderIntoDocument(