Simplifies catching keyboard interrupt

[sebromero]

This PR simplifies the process of catching the keyboard interrupt error reducing overhead.
Also it adds the option of running the loop non-blocking without delay. To do so the NON_BLOCKING property has to be set to True:

from arduino import *

arduino.NON_BLOCKING = True

def setup():
  print('setup test')

def loop():
  print('loop test')

def cleanup():
  print('cleanup test')

start(setup, loop, cleanup)

[ubidefeo]

Too fast:
please change the PR towards dev

[ubidefeo]

Merging