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/rgbled_pot_2.py

@@ -0,0 +1,11 @@
+from gpiozero import RGBLED, MCP3008
+from signal import pause
+
+led = RGBLED(2, 3, 4)
+red_pot = MCP3008(0)
+green_pot = MCP3008(1)
+blue_pot = MCP3008(2)
+
+led.source = zip(red_pot.values, green_pot.values, blue_pot.values)
+
+pause()