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/led_2.py

@@ -0,0 +1,8 @@
+from gpiozero import LED
+from signal import pause
+
+red = LED(17)
+
+red.blink()
+
+pause()