Update DallasTemperature.cpp

Updated blockTillConversionComplete to fix bug

Author: milesburton

DallasTemperature.cpp

@@ -337,15 +337,15 @@ bool DallasTemperature::requestTemperaturesByAddress(const uint8_t* deviceAddres
 
 // Continue to check if the IC has responded with a temperature
 void DallasTemperature::blockTillConversionComplete(uint8_t bitResolution, const uint8_t* deviceAddress){
-
+    
     int delms = millisToWaitForConversion(bitResolution);
     if (deviceAddress != NULL && checkForConversion && !parasite){
-        unsigned long timend = millis() + delms;
-        while(!isConversionAvailable(deviceAddress) && (millis() < timend));
-    }else{
+        unsigned long now = millis();
+        while(!isConversionAvailable(deviceAddress) && (millis() - delms < now));
+    } else {
         delay(delms);
     }
-
+    
 }
 
 // returns number of milliseconds to wait till conversion is complete (based on IC datasheet)