http://hackaday.com/2013/01/06/hardware-spi-with-python-on-a-raspberry-pi/
http://gammon.com.au/forum/?id=11516
http://louisthiery.com/spi-python-hardware-spi-for-raspi/
http://www.brianhensley.net/2012/07/getting-spi-working-on-raspberry-pi.html
http://raspi.tv/2013/8-x-8-led-array-driven-by-max7219-on-the-raspberry-pi-via-python
http://quick2wire.com/non-root-access-to-spi-on-the-pi