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.
? 'and use an HTTP server (instead of a file: URL) '
              : '') +
            'for a better development experience: ' +
            'https://fb.me/react-devtools',
        );
      }
    }
    var testFunc = function testFn() {};
    warning(
      (testFunc.name || testFunc.toString()).indexOf('testFn') !== -1,
      "It looks like you're using a minified copy of the development build " +
        'of React. When deploying React apps to production, make sure to use ' +
        'the production build which skips development warnings and is faster. ' +
        'See https://fb.me/react-minification for more details.',
    );
    
    
    var ieCompatibilityMode =
      document.documentMode && document.documentMode < 8;
    warning(
      !ieCompatibilityMode,
      'Internet Explorer is running in compatibility mode; please add the ' +
        'following tag to your HTML to prevent this from happening: ' +
        '<meta http-equiv="X-UA-Compatible" content="IE=edge" />',
    );
    var expectedFeatures = [
      
      Array.isArray,
      Array.prototype.every,
      Array.prototype.forEach,