+ /**
+ * A handy, and fast, way to traverse in a particular direction and find
+ * a specific element.
+ *
+ * @private
+ * @name $.nth
+ * @type DOMElement
+ * @param DOMElement cur The element to search from.
+ * @param Number|String num The Nth result to match. Can be a number or a string (like 'even' or 'odd').
+ * @param String dir The direction to move in (pass in something like 'previousSibling' or 'nextSibling').
+ * @cat DOM/Traversing
+ */