DHT22.cpp - DHT22 sensor library
  Developed by Ben Adams - 2011

Humidity and Temperature Sensor DHT22 info found at
http://www.sparkfun.com/products/10167

Version 0.41: 07-May-2012 added setPIN by JP Liew

Version 0.4: 24-Jan-2011 by Ben Adams
Added return code constants to keywords.txt
Returns DHT_ERROR_CHECKSUM on check sum mismatch 

Version 0.3: 17-Jan-2011 by Ben Adams
This version reads data
Needs check sum code added at the end of readData

Version 0.2: 16-Jan-2011 by Ben Adams
Changed coding style to match other Arduino libraries.
This version will not read data either!

Version 0.1: 10-Jan-2011 by Ben Adams nethoncho AT gmail.com
First Version is a skeleton. This version will not read data!
Code adapted from the following sources:
The Arduino OneWire lib
http://sheepdogguides.com/arduino/ar3ne1humDHT11.htm