Merge pull request #730 from dangreen/master

Throw error if call in node

Sortable.js

@@ -24,6 +24,12 @@
 })(function () {
 	"use strict";
 	
+	if (typeof window == "undefined" || typeof window.document == "undefined") {
+		return function() {
+			throw new Error( "Sortable.js requires a window with a document" );
+		}
+	}
+
 	var dragEl,
 		parentEl,
 		ghostEl,