Using gproc for interrupt registration works.
sim_gpio works as requested
Started on gpio.erl - need to take decisions about behaviour
Initial commit
Merge remote-tracking branch 'origin/master'
raising and falling interrupts work. both fails
forgot to store new value when checking interrupts in sim_gpio
Made the initial stub for the c node.

The c-node can now decode all the incomming arguments from gpio_if.erl except release which is not implemented at all.

There is no functionality in the c-node yet.
init and relase of a gpio pin now works on the pi
wrote code for writing to a gpio pin. Not working yet.
Fixed setting of gpio pin direction so turning on a LED works.
Reading from a GPIO pin now works
Initial stab at interrupts - stuck at pthread_tryjoin_np not defined for this architecture
Got interrupts to work - need to clean up the unnecessary code left in there
cleaned up the interrupt code
counting example for GPIO works.
added tests to repo
First test case passes with the single gpio module
Moved port commands into port_lib and parameterised CT test cases.
Refactored gpio_port_sim out of test suite