Install pyzbar to image (#225)

* Install pyzbar to image

I suggest installing pyzbar to RPi image for making barcodes scanning easier during different competitions.

* pyzbar: Add libzbar0 install

* pyzbar: Add simple tests

* pyzbar: Update docs

builder/test/tests.py

@@ -26,5 +26,6 @@ from pymavlink import mavutil
 import rpi_ws281x
 import pigpio
 from espeak import espeak
+from pyzbar import pyzbar
 
 print cv2.getBuildInformation()

builder/test/tests_py3.py

@@ -3,5 +3,6 @@
 # Make sure our Python 3 software is installed
 
 import cv2
+from pyzbar import pyzbar
 
 print(cv2.getBuildInformation())