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.
</svg>
            <image {...expectSVG} />
          </svg>
          <p {...expectHTML} />
        </div>,
      );
      assertNamespacesMatch(
        <div {...expectHTML}>
          <svg {...expectSVG}>
            <svg {...expectSVG}>
              <image {...expectSVG} />
              {usePortal(
                <svg {...expectSVG}>
                  <image {...expectSVG} />
                  <svg {...expectSVG}>
                    <image {...expectSVG} />
                  </svg>
                  <image {...expectSVG} />
                </svg>,
              )}
              <image {...expectSVG} />
              <foreignObject {...expectSVG}>
                <p {...expectHTML} />
                {usePortal(<p {...expectHTML} />)}
                <p {...expectHTML} />
              </foreignObject>
            </svg>
            <image {...expectSVG} />
          </svg>
          <p {...expectHTML} />