ApplyBindings now accepts DocumentFragments.

Allows situation like the following to work:

`
		var div = document.createElement("div");
		div.innerHTML = "<div data-bind='text: fooText'></div><div data-bind='text: barText'></div>"
		
		var frag = document.createDocumentFragment();
		frag.appendChild(div);
		
		var model = {
			fooText: ko.observable("foo"),
			barText: ko.observable("bar")
		}
		
		ko.applyBindings(model, frag);
		document.body.appendChild(frag);
`