Adding template bindings for border on the flat button style. Previously these were un-used.

Author: Keboo

MaterialDesignThemes.Wpf/Themes/MaterialDesignTheme.Button.xaml

@@ -105,7 +105,8 @@
             <Setter.Value>
                 <ControlTemplate TargetType="{x:Type Button}">
                     <Grid>
-                        <Border Background="{TemplateBinding Background}" x:Name="border" CornerRadius="2">
+                        <Border Background="{TemplateBinding Background}" x:Name="border" CornerRadius="2"
+                                BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}">
                             <wpf:Ripple Content="{TemplateBinding Content}" ContentTemplate="{TemplateBinding ContentTemplate}" Focusable="False"    
                                         HorizontalContentAlignment="{TemplateBinding HorizontalContentAlignment}" 
                                         VerticalContentAlignment="{TemplateBinding VerticalContentAlignment}"