Wrap around several (in the future anyway) low-level GPIO python modules to make development and porting easier.

Current backend targets, in decreasing importance, are: * RPi.GPIO (Raspberry Pi, https://pypi.python.org/pypi/RPi.GPIO) * SUNXI_GPIO (Cubiboard A10, https://github.com/ruisebastiao/pySUNXI) * Linux's sysfs (all supported platforms (?))

The provided Application class is only meant as a demonstration of how to implement ggpio into a multithreaded application.