Added public "needsFallback" method

Hi, this is a great project.

I've made a small modification. I needed to know whether the fallback would be used because I have my own code that manages the document title. I extracted that check into a method which I then exposed in the public API. Seems like it might be useful to others. (I'm not particularly attached to the method name, "needsFallback", btw.)

PS, I didn't include the minified file in this request -- the one I generated was quite different from the original.

Thanks,
Alex