Merge pull request #4 from stevenbell/patch-1

Cast to int32 so that negative values work

Author: aentinger

src/MKRTHERM.cpp

@@ -94,7 +94,7 @@ float THERMClass::readTemperature()
     rawword >>= 18;
   }
   // multiply for the LSB value
-  celsius = rawword * 0.25f;
+  celsius = (int32_t)rawword * 0.25f;
 
   return celsius;
 }