Adds support for a "hover" event. The event provides a convenience wrapper for subscribing separately to mouseenter and mouseleave. The signature for subscribing to the event is

node.on("hover", overFn, outFn);
node.delegate("hover", overFn, outFn, ".filterSelector");
Y.on("hover", overFn, outFn, ".targetSelector");
Y.delegate("hover", overFn, outFn, "#container", ".filterSelector");

Additionally, for compatibility with a more typical subscription signature, the following are also supported:

Y.on("hover", overFn, ".targetSelector", outFn);
Y.delegate("hover", overFn, "#container", outFn, ".filterSelector");