Returns a collection of the collection’s last child element.
var svg = Pablo(demoElement).svg({height: 60});
svg.append(Pablo.circle({r: 30, cx: 30, cy: 30}))
.append(Pablo.circle({r: 30, cx: 100, cy: 30}))
.append(Pablo.circle({r: 30, cx: 170, cy: 30}));
svg.lastChild().attr({'fill':'green'})