Add debounce option

[tikismoke]

Avoid user to add a 0.1uF on switch:

To debounce using software, add the bouncetime= parameter to a function where you specify a callback function. Bouncetime should be specified in milliseconds. For example:

add rising edge detection on a channel, ignoring further edges for 200ms for switch bounce handling
GPIO.add_event_detect(channel, GPIO.RISING, callback=my_callback, bouncetime=200)

[tikismoke]

After using the callback from #1