incorporates suggestions

proposed changes

Author: csylvain

examples/tsl2561_simpletest.py

@@ -43,10 +43,10 @@
 print("Integration time = {}".format(tsl.integration_time))
 print("Broadband = {}".format(broadband))
 print("Infrared = {}".format(infrared))
-if lux != None:
+if lux is not None:
     print("Lux = {}".format(lux))
 else:
-    print("Lux = NaN")
+    print("Lux value is None. Possible sensor underrange or overrange.")
 
 # Disble the light sensor (to save power)
 tsl.enabled = False