Lowest form of communication with the GPIO pins. The available pins are listed in the "channel" parameter, and appear as directories in /sys/class/gpio after being exported. For instance, to setup a GPIO on "gpio112", configure it as an output pin and set it to high, the following code would be used.
```
gpio = GPIO(1)
write!(gpio, (2,"out"))
write!(gpio, (1, "1"))
`gpio = GPIO(1)`
`write!(gpio, (2,"out"))`
`write!(gpio, (1, "1"))`
```
The operation of reading the current output value of the GPIO is done by
```
read(gpio, 1)
`read(gpio, 1)`
```
See the test/BeagleBone/GPIO_test.jl for more examples.