Convert recipe examples to includes

Makes it much easier to test things - no copying'n'pasting just run the
examples straight from the dir (after wiring stuff up)

docs/examples/all_on_2.py

@@ -0,0 +1,9 @@
+from gpiozero import TrafficHat
+from signal import pause
+
+th = TrafficHat()
+
+th.button.when_pressed = th.on
+th.button.when_released = th.off
+
+pause()