Make Iterator a daemon for proper exit

Conflicts:
	pyfirmata/util.py

pyfirmata/util.py

@@ -2,7 +2,7 @@
 from __future__ import unicode_literals
 import threading
 import time
-import os
+import os, sys
 
 import serial
 
@@ -39,6 +39,7 @@ class Iterator(threading.Thread):
     def __init__(self, board):
         super(Iterator, self).__init__()
         self.board = board
+        self.daemon = True
 
     def run(self):
         while 1:
@@ -63,6 +64,8 @@ def run(self):
                     pass
                 raise
 
+            except (KeyboardInterrupt) as e:
+                sys.exit()
 
 def to_two_bytes(integer):
     """