private async void rangLista_Click(object sender, RoutedEventArgs e)
        {
            StorageFolder folder = ApplicationData.Current.LocalFolder;
            StorageFile sampleFile = await folder.CreateFileAsync("rekordi.txt", CreationCollisionOption.OpenIfExists);
            var lines = await FileIO.ReadLinesAsync(sampleFile);

            string rangPrikaz = "";
            foreach (var line in lines)
            {
                rangPrikaz += line.ToString();
            }

            MessageDialog msg = new MessageDialog(rangPrikaz);
            msg.ShowAsync();
        }