Added Polyfill for Firefox 3.5-21 support.

While Firefox 22 is just around the corner there has been a polyfill around for a while, and now that I know of CanIUse I thought it should be added to the list.
Does not qualify as a polyfill, Please add link anyway.
Merge pull request #204 from MailYouLater/patch-2

Added Polyfill for Firefox 3.5-21 support.