Fixed DS18B20 handling because of new floating point handling

Hi,

because of the new floating point API, the old ds18b20 code returns strange values like "19.8250.8250". 
This change fixes that. 

Best regards,
Tobias

lua_modules/ds18b20/ds18b20.lua

@@ -105,11 +105,10 @@ function readNumber(addr, unit)
         else
           return nil
         end
-        t1 = t / 10000
+        t = t / 10000
-        t2 = t % 10000
         -- print("Temperature="..t1.."."..t2.." Centigrade")
         -- result = t1.."."..t2
-        return t1, t2
+        return t
       end
       tmr.wdclr()
     else
@@ -122,11 +121,11 @@ function readNumber(addr, unit)
 end
 
 function read(addr, unit)
-  t1, t2 = readNumber(addr, unit)
+  t = readNumber(addr, unit)
-  if((t1 == nil ) or (t2 ==nil)) then
+  if (t == nil) then
     return nil
   else
-    return t1.."."..string.format("%04u", t2)
+    return t
   end
 end