Noted API return values in doc comments.
Changed mouse-event check to use typeof.

Although unlikely in the real world, it is possible for event.pageX to
be 0. Related to pull request #75.
Changed close events to immediate for all non-mouse events.

The only events that we can be sure require close delays are mouse
events. Related to pull request #75.
Simplified the core event's argument conditionals.

Crockford would probably say this adds "trickiness", but somehow it
looks more readable to my eyes. Related to pull request #75.
Moved showHide() code to new API toggle() method.

Part of issue #95. Changes code added in pull request #75.
Refactored core event handlers into event declarations.

This commit changes the event handlers used in the default events to be
private. It also slightly reduces the minified file size. Related to
pull request #75.
Renamed core event handler functions.

This is just a minor readability improvement, there are no behavior
changes.
Wrapped comments to 80 characters.
Added toggle() assertion to expose API tests.

Part of issue #95
Added mouse event checking to API show() method.

This will prevent this function from throwing an error if it receives a
non-mouse event.
Removed mouse event check from elementOpen.

This is no longer needed since the check was added to the API show()
method in commit edfb6d65d67074a62da60c6a7d252c61564d1b03.