Add CAN Test and Schematics

This adds a test which sends a uint8 CAN message from CAN0 to CAN1. I
have used this to verify my dual CAN transceiver board works properly.

Schematics from
http://forum.arduino.cc/index.php?PHPSESSID=24kmf0sjr7pd32l2nor9toqvm6&t
opic=131096.msg1011501#msg1011501

CAN test code based off Arduino CAN library, example 1.