[avr-chat] lesson/demo modules for cduino

[Britton Kerin]

Chris Kuethe contributed a really nice series of demos/lessons
covering a variety
of AVR subsystems:

http://brittonkerin.com/cduino/lessons.html

I've added them as modules to cduino (http://brittonkerin.com/cduino/).

More topics to come soon (on analog input, interrupts, persistent storage,
and the watchdog timer).

For those who don't want to wait Chris' (slightly different) original material
is available here: https://www.mainframe.cx/~ckuethe/avr-c-tutorial/