Fix #37 by optimizing pulse read to use direct port access on AVR, stops checksum failures from missed signals.

DHT.h

@@ -48,8 +48,8 @@ class DHT {
 
  private:
   uint8_t data[6];
-  uint8_t _pin, _type;
-  uint32_t _lastreadtime;
+  uint8_t _pin, _type, _bit, _port;
+  uint32_t _lastreadtime, _maxcycles;
   bool _firstreading;
   bool _lastresult;