Add button adapter to run program without Raspberry Pi

[kashev]

It would be nice to be able to run morse-code-twitter on a normal computer without RPi GPIO, for testing purposes. We can do this by breaking the logic between the Morse Code handling, the RPi Button Handling, and adding a keyboard button through a library like pygame. Some research will be required to figure out the best way to do this.

[kashev]

branch separate_logic starts to work on this, breaks the button callback logic away from the actual RPI GPIO. Another class could be written to be a regular computer adapter so long as keyup and keydown events could call callback with appropriate arguments.