message: The selected tabs should be a different color
diff: <mah:HamburgerMenu.Content>
  <Grid>
  + <Rectangle Fill="{DynamicResource MahApps.Brushes.Gray8}"
  + VerticalAlignment="Top"
  + HorizontalAlignment="Stretch"
  + Height="28" />
  <TabControl
  Grid.Row="0"
  Background="{DynamicResource MahApps.Brushes.ThemeBackground}"
  </Grid.RowDefinitions>
  <Border x:Name="HeaderPanel"
  Grid.Row="0"
  - Background="{DynamicResource MahApps.Brushes.Gray8}"
  BorderThickness="0"
  KeyboardNavigation.DirectionalNavigation="Contained"
  KeyboardNavigation.TabIndex="2"
  </Border>
  <Border x:Name="ContentPanel"
  Grid.Row="1"
  - Background="{TemplateBinding Background}"
  - BorderBrush="{TemplateBinding BorderBrush}"
  BorderThickness="0"
  KeyboardNavigation.DirectionalNavigation="Contained"
  KeyboardNavigation.TabIndex="2"
  