subclass of Class
associate help with a widget such as a button. A box with the help text in it
will popup after staying for some time over the widget without doing anything.
Balloon is not meant to be instanciated; the command can can rather be used
directly from the class.
Balloon private time ms
set the time (in miliseconds) to wait before the helptext gets displayed
Balloon add widget text
add $text as help to the given widget
Balloon display widget
display the helptext associated with $widget
remove the currently displayed helptext