Initial Commit (tylerb version)

gpio.go defines an interface that can be used to interact with any conforming driver implementation.
linux/linux.go provides an interface for the /sys driver
examples/blink/blink.go blinks an LED on pin 25 using the linux /sys driver
Integrate davecheney change suggestions
Fixed a few problems
Cleaning things up a bit
Hold value FD open
Update example to use updated interface
Fix a few problems