Delay for longer before listening for signal

Delay for 50 us not 10 us after pulling data line low. This change is taken from
a comment on Issue 48 (adafruit#48)
of the Adafruit library (https://github.com/adafruit/DHT-sensor-library)

Reference: adafruit#48 (comment)

Author: Perseudonymous

DHT.cpp

@@ -161,7 +161,7 @@ boolean DHT::read(bool force) {
 
     // Now start reading the data line to get the value from the DHT sensor.
     pinMode(_pin, INPUT_PULLUP);
-    delayMicroseconds(10);  // Delay a bit to let sensor pull data line low.
+    delayMicroseconds(50);  // Delay a bit to let sensor pull data line low.
 
     // First expect a low signal for ~80 microseconds followed by a high signal
     // for ~80 microseconds again.