Refactored core event handlers into event declarations.
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.

jasco/jquery-powertip,erthalion/jquery-powertip,jasco/jquery-powertip,erthalion/jquery-powertip,stevenbenner/jquery-powertip,stevenbenner/jquery-powertip