Don't reference `Tether` via attachment to `window`, with the update one can import bootstrap providing the dependencies in webpack with:

```
new webpack.ProvidePlugin({
  $: 'jquery',
  jQuery: 'jquery',
  Tether: 'tether',
});
```

Then inside one's own bootstrap/globals, `import 'bootstrap';` will simply work, and $/jQuery can be used from there.

I had wanted to do this, but also expose jQuery, Tether, etc when in development build in my code, but if I provide `window.Tether`, I can't then expose it to the outside...