Packaging error: minified dist file is empty

[`dist/typestate-1.0.6.min.js`](https://cdn.jsdelivr.net/npm/typestate@1.0.6/dist/typestate-1.0.6.min.js) is empty (apart from comments).

```sh
$ cat dist/typestate-1.0.6.min.js
```

```javascript
/*! typestate - v1.0.6 - 2018-05-17
* https://github.com/eonarheim/TypeState
* Copyright (c) 2018 Erik Onarheim; Licensed BSD-2-Clause*/
```