I'll definitely re-work on both the code and the doc. I've read that there is a kind of localStorage portage for IE8- that I'll look into.
Currently, if the browser does not support localStorage, the plugin auto-disable.
Which leads me to an aside — Why did you choose localStorage over sessionStorage?
For those who don't know — local/session are the same, only session will be cleared when the browser is closed.
My browser already auto completes form data… so I'm not sure I'd need it between sessions.