optional delay before serial program

Note, this is commented out by default, but will be needed for doing any serial programming to micros that need a sec to enumerate the com port. See the following comment thread on the tutorial for more info about how the problem was discovered/fixed

[https://learn.sparkfun.com/tutorials/raspberry-pi-stand-alone-programmer/discuss#comment-5ab2d42d7e7fa89f378b4567](https://learn.sparkfun.com/tutorials/raspberry-pi-stand-alone-programmer/discuss#comment-5ab2d42d7e7fa89f378b4567)

Author: Pete Lewis

test.py

@@ -429,6 +429,8 @@ def blink_all():
                 program()
                 parse_results()
                 if ((os.path.exists('/home/pi/SERIAL_UPLOAD/pi_serial_upload.sh') == True) and (LOCK_BITS_PASS == True)):
+                        # time.sleep(1) # Delay to allow com port enumeration.
+                        # Note, this delay is only needed with micros that have USB capabilities (like the atmega32u4)
                         program_serial()
                         parse_results_serial()
                         time.sleep(3) # led leds stay on for 3 secs