Merge README.md change from pull #43

Author: tdicola

README.txt renamed to README.md

@@ -1,3 +1,5 @@
 This is an Arduino library for the DHT series of low cost temperature/humidity sensors. 
 
-To download. click the DOWNLOADS button in the top right corner, rename the uncompressed folder DHT. Check that the DHT folder contains DHT.cpp and DHT.h. Place the DHT library folder your <arduinosketchfolder>/libraries/ folder. You may need to create the libraries subfolder if its your first library. Restart the IDE.
+Tutorial: https://learn.adafruit.com/dht
+
+To download. click the DOWNLOADS button in the top right corner, rename the uncompressed folder DHT. Check that the DHT folder contains DHT.cpp and DHT.h. Place the DHT library folder your <arduinosketchfolder>/libraries/ folder. You may need to create the libraries subfolder if its your first library. Restart the IDE.