Update spi/README.md

SDA doesn't figure in the text, only the datasheet.

According to http://elinux.org/RPi_BCM2835_GPIOs, SPI0 has only 2 chip selects.
The datasheet mentions a Chip Select 2 for the CS register, but this appears to be an error.
Fix the build task
Ignore gem lock
Show rendered count
Add image alt text
Fix broken power link
Fix broken cron link
Fix broken power link and issues internal link
Fix broken raspi-config link
Fix broken power link
Add internal anchors and update RyanTeck link
Merge pull request #107 from penibelst/fix-build

Fix the build task
Merge pull request #99 from notro/master

Update spi/README.md
Add image alt text

images are still missing though!
Add missing PuTTY images
Added pin configuration documentation
Compute module camera instructions update
Updated default pin configuration