added comments to button.c
added comments to button.c

chaicko/ExploringBeagleBone,chaicko/ExploringBeagleBone,chaicko/ExploringBeagleBone,chaicko/ExploringBeagleBone,chaicko/ExploringBeagleBone,chaicko/ExploringBeagleBone,chaicko/ExploringBeagleBone,chaicko/ExploringBeagleBone,chaicko/ExploringBeagleBone,chaicko/ExploringBeagleBone