Error after following typescript example with React 16.4.1

If you are reporting a bug or having an issue setting up React Hot Loader, please fill in below. For feature requests, feel free to remove this template entirely.

### Description

```
react-hot-loader.development.js:227 Uncaught TypeError: Class constructor App cannot be invoked without 'new'
at new App (react-hot-loader.development.js:227)
at constructClassInstance (react-dom.development.js:11447)
at updateClassComponent (react-dom.development.js:13144)
at beginWork (react-dom.development.js:13824)
at performUnitOfWork (react-dom.development.js:15863)
at workLoop (react-dom.development.js:15902)
at HTMLUnknownElement.callCallback (react-dom.development.js:100)
at Object.invokeGuardedCallbackDev (react-dom.development.js:138)
at invokeGuardedCallback (react-dom.development.js:187)
at replayUnitOfWork (react-dom.development.js:15310)
```

### Expected behavior

Web page is rendered.

### Actual behavior

The error above is created

### Environment

React Hot Loader version: 4.3.3

Run these commands in the project folder and fill in their results:

1. `node -v`: 8.11.3
2. `npm -v`: (yarn 1.7.0

Then, specify:

1. Operating system: Osx.
2. Browser and version: Chrome latest. Assets built for latest 2 versions of chrome

### Reproducible Demo

Please take the time to create a new project that reproduces the issue.

Will get this ASAP but posting now in the off change this is something obvious.