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/

expect(node.value).toEqual('true');
  });
  it('should allow setting `value` to `false`', function() {
    var container = document.createElement('div');
    var stub = <input type="text" value="yolo" onChange={emptyFunction} />;
    var node = ReactDOM.render(stub, container);
    expect(node.value).toBe('yolo');
    stub = ReactDOM.render(
      <input type="text" value={false} onChange={emptyFunction} />,
      container
    );
    expect(node.value).toEqual('false');
  });
  it('should allow setting `value` to `objToString`', function() {
    var container = document.createElement('div');
    var stub = <input type="text" value="foo" onChange={emptyFunction} />;
    var node = ReactDOM.render(stub, container);
    expect(node.value).toBe('foo');
    var objToString = {
      toString: function() {
        return 'foobar';
      },
    };
    stub = ReactDOM.render(
      <input type="text" value={objToString} onChange={emptyFunction} />,
      container
    );
    expect(node.value).toEqual('foobar');
  });
  it('should not incur unnecessary DOM mutations', function() {