Currently if React is not loaded, ReactDOM shows this:

<img width="664" alt="screen shot 2017-08-08 at 3 36 52 pm" src="https://user-images.githubusercontent.com/810438/29077217-784c7624-7c4f-11e7-88bc-b055407523a9.png">

We should throw a nicer error message in the entry point I think.
parentNamespace,
    );
    precacheFiberNode(internalInstanceHandle, domElement);
    updateFiberProps(domElement, props);
    return domElement;
  },
  appendInitialChild(
    parentInstance: Instance,
    child: Instance | TextInstance,
  ): void {
    parentInstance.appendChild(child);
  },
  finalizeInitialChildren(
    domElement: Instance,
    type: string,
    props: Props,
    rootContainerInstance: Container,
  ): boolean {
    setInitialProperties(domElement, type, props, rootContainerInstance);
    return shouldAutoFocusHostComponent(type, props);
  },
  prepareUpdate(
    domElement: Instance,
    type: string,
    oldProps: Props,
    newProps: Props,
    rootContainerInstance: Container,
    hostContext: HostContext,
  ): null | Array<mixed> {
    if (__DEV__) {