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.
rootContainerInstance,
    );
  },
  commitMount(
    domElement: Instance,
    type: string,
    newProps: Props,
    internalInstanceHandle: Object,
  ): void {
    ((domElement: any):
      | HTMLButtonElement
      | HTMLInputElement
      | HTMLSelectElement
      | HTMLTextAreaElement).focus();
  },
  commitUpdate(
    domElement: Instance,
    updatePayload: Array<mixed>,
    type: string,
    oldProps: Props,
    newProps: Props,
    internalInstanceHandle: Object,
  ): void {
    
    
    updateFiberProps(domElement, newProps);
    
    updateProperties(domElement, updatePayload, type, oldProps, newProps);
  },
  shouldSetTextContent(type: string, props: Props): boolean {