This release implements the concept of "touching" points on the
chart with a mouse-centered, point selection "brush". The pop-up
annotations that appear when each point is touched can be quickly
configured via the new HTML hovertext template facility. Or, with a
bit more effort, any GWT Widget (including another GChart) can be
turned into such a pop-up by implementing GChart's new
HoverUpdateable interface.  Finally, appropriate actions can be
taken whenever the user clicks on a point, since GChart now
implements GWT's SourcesClickEvents interface. The updated live
demo illustrates all of these techniques. See the 2.4 release notes 
for a complete change list, with links to the new features' javadocs 
and example code. 
