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:

componentWillReceivePropsParams.push(...args);
        this.setState((...innerArgs) => {
          setStateParams.push(...innerArgs);
          return updatedState;
        });
      }
      UNSAFE_componentWillUpdate(...args) {
        componentWillUpdateParams.push(...args);
      }
      shouldComponentUpdate(...args) {
        shouldComponentUpdateParams.push(...args);
        return true;
      }
      render() {
        return null;
      }
    }
    const shallowRenderer = createRenderer();
    shallowRenderer.render(
      React.createElement(SimpleComponent, initialProp),
      initialContext,
    );
    expect(componentDidUpdateParams).toEqual([]);
    expect(componentWillReceivePropsParams).toEqual([]);
    expect(componentWillUpdateParams).toEqual([]);
    expect(setStateParams).toEqual([]);
    expect(shouldComponentUpdateParams).toEqual([]);
    
    shallowRenderer.render(