When loading via plain script tag FileSaver.saveAs is not a function. Again.

When loading dist/FileSaver.js via ``, `FileSaver.saveAs()` is not available. Here are the facts:

- `FileSaver` is an empty object `{}`
- `_global`, which refers to the `Window` object is in the global namespace
- `saveAs()` is also in the global namespace, rather than as a member of `FileSaver`

The culprit is in the packaging:

https://github.com/eligrey/FileSaver.js/blob/be09a02e8cd3fe7046a692b19f6aa9631d0146c7/dist/FileSaver.js#L7-L11

Note that:

1. `mod.exports` is set to empty object `{}`
2. Then `factory()` is called _without arguments_, and is thus unable to populate `mod.exports` as that reference is out of scope.
3. Finally, `window.FileSaver` is set to `mod.exports`, **which is an empty object `{}` at this point**.
4. Thus, `FileSaver` is just an empty object. This seems like a bug.

If this in intended behavior, it clashes with the docs. The only way to use `FileSaver` in a page that does not have module infrastructure is to use `window.saveAs()`, which seems really strange. Probably risky too of getting clobbered by some other library.

This seems related to #253, which was closed by @jimmywarting, presumably after a fix. However, this seems to be new behavior that is plaguing `v2.0.0`.

If this behavior is intentional, it's certainly strange (and where is it documented)?