add css styling to buttons, fixes ilgarmehmetali#16

src/BudgiePixelSaverApplet.vala

@@ -64,6 +64,7 @@ public class Applet : Budgie.Applet
         this.applet_container.pack_start (this.close_button, false, false, 0);
         this.add (this.applet_container);
 
+        this.set_css_styles();
 
         event_box.button_press_event.connect ((event) => {
             if (event.type == Gdk.EventType.@2BUTTON_PRESS){
@@ -139,6 +140,19 @@ public class Applet : Budgie.Applet
         this.title_bar_manager.unregister();
     }
 
+    private void set_css_styles(){
+        this.applet_container.get_style_context().add_class("titlebar");
+
+        this.minimize_button.get_style_context().add_class("titlebutton");
+        this.minimize_button.get_style_context().add_class("minimize");
+
+        this.maximize_button.get_style_context().add_class("titlebutton");
+        this.maximize_button.get_style_context().add_class("maximize");
+
+        this.close_button.get_style_context().add_class("titlebutton");
+        this.close_button.get_style_context().add_class("close");
+    }
+
     void on_settings_change(string key) {
         if (key == "size") {
             this.label.set_max_width_chars(settings.get_int(key));