1) Changed from DISPLAY to DBUS_SESSION due to lack of notification on
kubuntu 14.04

# c/o
http://askubuntu.com/questions/298608/notify-send-doesnt-work-from-crontab

2) Added paths to commands

3) Simplified go_send* to single function and create 'at' jobs under
kid's id instead of root's.

4) Add icons to remove gnome dependency and provide a visual countdown.
The icons are a derivative work of ktimer.png from ktimer which is GPL
http://www.kde.org/applications/utilities/ktimer/, Stefan Schimanski
<schimmi@kde.org> is the original author)