Added (messy) code for CAN library
-MCP2515_defs_extended.h has defs for filter/mask registers
-CAN_IO.h is basically a copy of the specs in the google doc Alexander
sent out
-CAN_IO.cpp has very tentative implementations for part of CAN_IO.h
-CAN_test.cpp is intended for testing CAN code
Merge branch 'master' of https://github.com/nusolar/sc7-arduino-code