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.
canHydrateTextInstance(
    instance: Instance | TextInstance,
    text: string,
  ): boolean {
    if (text === '') {
      
      return false;
    }
    return instance.nodeType === TEXT_NODE;
  },
  getNextHydratableSibling(
    instance: Instance | TextInstance,
  ): null | Instance | TextInstance {
    let node = instance.nextSibling;
    
    while (
      node &&
      node.nodeType !== ELEMENT_NODE &&
      node.nodeType !== TEXT_NODE
    ) {
      node = node.nextSibling;
    }
    return (node: any);
  },
  getFirstHydratableChild(
    parentInstance: Container | Instance,
  ): null | Instance | TextInstance {
    let next = parentInstance.firstChild;
    
    while (