Fix shebangs and permissions

The scripts have a mix of no shebang, python and python3 (a relatively
harmless difference). They are also not all executable, which is worse,
as users appear to:

- run the script
- get permission denied
- run the script with sudo
- start superstitiously using sudo
- break the virtualenv by using sudo

cf:
#238 (comment)

Change-Id: I5d53b147f806d2318668d147bfd42f757692380d

src/examples/vision/annotator.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 # Copyright 2017 Google Inc.
 #
 # Licensed under the Apache License, Version 2.0 (the "License");

src/examples/vision/dish_classifier.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 # Copyright 2017 Google Inc.
 #
 # Licensed under the Apache License, Version 2.0 (the "License");

src/examples/vision/gpiozero/button_example.py

@@ -1,3 +1,4 @@
+#!/usr/bin/env python3
 """Example code that demonstrates using a standard pin along with a hat pin.
 
 The button uses a standard GPIO pin through the raspberry pi's memory mapped io,

src/examples/vision/gpiozero/hat_button.py

@@ -1,3 +1,4 @@
+#!/usr/bin/env python3
 """Example code that demonstrates using a button connected through the hat.
 
 The button uses a hat pin through the sysfs driver illustrating the edge

src/examples/vision/gpiozero/led_example.py

@@ -1,3 +1,4 @@
+#!/usr/bin/env python3
 """Demonstrates on board LED support with correct polarity.
 
 Demo will turn on, then off the first LED on the hat.

src/examples/vision/gpiozero/servo_example.py

@@ -1,3 +1,4 @@
+#!/usr/bin/env python3
 """Demonstrates simultaneous control of two servos on the hat.
 
 One servo uses the simple default configuration, the other servo is tuned to

src/examples/vision/gpiozero/simple_button_example.py

@@ -1,3 +1,4 @@
+#!/usr/bin/env python3
 """Example code that demonstrates using a standard pin along with a hat pin.
 
 The button uses a standard GPIO pin through the raspberry pi's memory mapped io,

src/examples/vision/leds_example.py

@@ -1,3 +1,4 @@
+#!/usr/bin/env python3
 # Copyright 2018 Google Inc.
 #
 # Licensed under the Apache License, Version 2.0 (the "License");

src/examples/vision/object_detection_camera.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 # Copyright 2017 Google Inc.
 #
 # Licensed under the Apache License, Version 2.0 (the "License");

src/examples/vision/object_meter/wordnet_grouping/category_mapper.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 # Copyright 2018 Google Inc.
 #
 # Licensed under the Apache License, Version 2.0 (the "License");

src/examples/vision/object_meter/wordnet_grouping/mapping_data.py

@@ -1,4 +1,3 @@
-#!/usr/bin/env python
 # Copyright 2018 Google Inc.
 #
 # Licensed under the Apache License, Version 2.0 (the "License");