Moving pending work to pending dir and update README
Fix requires
prevent instance.publish() from updating static event
configure(ET) and make ET default events from ET.events

EventTarget wasn't being configure()d, so subclassing couldn't take advantage
of default events from EventTarget. Also, the EventTarget constructor was
creating the _yuievt.events collection as a bare object if the class wasn't
configure()d, which would leave an instance without a default or base event.
With EventTarget configure()d, the constructor could now fall back to the
EventTarget.events collection, so all instances will have base and default
events.
configure() only works for classes now

Since EventTarget constructor creates the _yuievt.events collection from the
constructor.events, and as an EventTarget, it had a `publish()` method, it
didn't make sense to configure an instance. If instances want to override their
base and default events, they can `publish()` them.
Prune objects on unsubscribe + more

And break out getDynamicEvent for DYNAMIC_DEFAULT to make it easier for
derived events (such as Y.Event's default event) to incorporate it into their
subscribe logic.
Add isEventSupported(type) + more

The Y.Event default event now supports subscribing to and detaching from
custom events if the subscribed event name isn't in Y.Node.NODE_EVENTS or,
if 'node' isn't loaded, Y.Event.isEventSupported(type) returns false.

It will be a rare case that 'node' won't be loaded so this is a bit of code
weight, but the complexity should be about the same.

Also cleaned up the subscribe and unsubscribe code and made unsubscribe remove
the DOM event listener when the last subscriber is removed.
typo fix and immediate() needed a Subscription :(