do not convert *_MODE metrics from/to celcius when key contains _TEMP_ (

#5)

index.js

@@ -146,7 +146,7 @@ module.exports = class Vallox {
 
     keys.forEach(key => {
       const value = vlxReceiveBuffer[calculateOffset(VlxDevConstants[key])]
-      result[key] = key.indexOf('_TEMP_') === -1 ? value : this._toCelsius(value)
+      result[key] = this.convert(key, value, () => this._toCelsius(value))
     })
 
     return result
@@ -160,12 +160,16 @@ module.exports = class Vallox {
       const item = new VlxWriteItem()
 
       item.address = VlxDevConstants[key]
-      item.value = key.indexOf('_TEMP_') === -1 ? value : this._toKelvin(value)
+      item.value = this.convert(key, value, () => this._toKelvin(value))
       buf.appendData(item)
     })
 
     await this._request(buf.convertDataToBuffer(VlxDevConstants.WS_WEB_UI_COMMAND_WRITE_DATA))
 
     return true
   }
+
+  convert (key, value, converter) {
+    return (key.indexOf('_TEMP_') === -1 || key.indexOf('_MODE') > 0) ? value : converter()
+  }
 }