Documentation fix: window.location should be window.history

[JohnRiv]

Looks like this was actually previously fixed via 70d9799 but it was then reverted by tedium-bot when it autogenerated the README file in 2e2fa64.

It's unclear to me from the outside how tedium-bot did the autogeneration, so if there is another spot I need to make this change (and I can access it), let me know.