message: Use plain black for timer drop shadow (win)
diff: <Border Grid.Row="0" Height="1" VerticalAlignment="Bottom"
  Background="{Binding ElementName=Timer, Path=Background}">
  <Border.Effect>
  - <DropShadowEffect Direction="270" Color="{DynamicResource Toggl.BlackColor}" Opacity="0.2"
  + <DropShadowEffect Direction="270" Color="Black" Opacity="0.2"
  BlurRadius="4" ShadowDepth="1" />
  </Border.Effect>
  </Border>
  