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.
): HostContext {
    if (__DEV__) {
      const parentHostContextDev = ((parentHostContext: any): HostContextDev);
      const namespace = getChildNamespace(parentHostContextDev.namespace, type);
      const ancestorInfo = updatedAncestorInfo(
        parentHostContextDev.ancestorInfo,
        type,
        null,
      );
      return {namespace, ancestorInfo};
    }
    const parentNamespace = ((parentHostContext: any): HostContextProd);
    return getChildNamespace(parentNamespace, type);
  },
  getPublicInstance(instance) {
    return instance;
  },
  prepareForCommit(): void {
    eventsEnabled = ReactBrowserEventEmitter.isEnabled();
    selectionInformation = ReactInputSelection.getSelectionInformation();
    ReactBrowserEventEmitter.setEnabled(false);
  },
  resetAfterCommit(): void {
    ReactInputSelection.restoreSelection(selectionInformation);
    selectionInformation = null;
    ReactBrowserEventEmitter.setEnabled(eventsEnabled);
    eventsEnabled = null;
  },
  createInstance(
    type: string,