Clarify pin number for Raspberry Pi

Referencing the pin by "GPIO23" is clearer than referencing by "pin 23", as GPIO23 is physical pin 16.

Author: Mazo

examples/simpletest.py

@@ -31,7 +31,7 @@
 pin = 'P8_11'
 
 # Example using a Raspberry Pi with DHT sensor
-# connected to pin 23.
+# connected to GPIO23.
 #pin = 23
 
 # Try to grab a sensor reading.  Use the read_retry method which will retry up