function removeClass(element, className) {
    if (element instanceof Element) {
        if (element.classList) {
            element.classList.remove(className);
        } else {
            // TODO: Need some jsperf tests on performance - can we get rid of the regex and maybe use split / array manipulation?
            element.className = element.className.replace(new RegExp("(^|\\s)" + className + "(\\s|$)", "gi"), " ");
        }
    }
}
Remove a single className from an Element.