We're switching Atom to React, but we want to support backward-compatible shims to our previous view framework.

In the old framework, views were represented as jQuery-wrapped DOM elements. Ideally, we'd like to provide backward-compatible shims by simply rendering the React component and wrapping its root element in a jQuery wrapper with an API that's compatible to our old editor views. That would essentially look like this:

``` javascript
var editorRoot = document.createElement('div')
React.renderComponentWithRootElement(Editor(props), editorRoot)

// the element would actually be wrapped in a custom subclass of jQuery,
// but this is clearer for this example
var editorShim = $(editorRoot) 
```

Currently, this isn't possible because React components need to be rendered into a container. So instead we need to create a wrapper element and render the component inside it. This is sad because it adds an extra layer of markup which confuses styling, and also means that the editor has a wrapper when used via the shim layer but no wrapper when embedded as a child via React itself.

Is there something fundamental preventing React from adopting DOM nodes directly without the parent? Is this something we could even hack in in a way that would be somewhat maintainable?

:heart:

state = {value: 0};
      handleChange = value => {
        this.setState({value});
      };
      render() {
        return <Child remote={this.state.value} onChange={this.handleChange} />;
      }
    }
    const container = document.createElement('div');
    document.body.appendChild(container);
    try {
      ReactDOM.render(<Parent />, container);
      expect(divRef.current.textContent).toBe('remote:0, local:0');
      
      childInstance.updateState();
      expect(divRef.current.textContent).toBe('remote:1, local:1');
      
      divRef.current.click();
      expect(divRef.current.textContent).toBe('remote:2, local:2');
    } finally {
      document.body.removeChild(container);
    }
  });
  it('should pass the return value from getSnapshotBeforeUpdate to componentDidUpdate', () => {
    const log = [];
    class MyComponent extends React.Component {