use modern (2018) pattern for modules

src/browser/header/tray/tab.rs

@@ -0,0 +1,23 @@
+use gtk::Button;
+
+pub struct Tab {
+    pub widget: Button,
+}
+
+impl Tab {
+    // Construct
+    pub fn new() -> Self {
+        Self {
+            widget: Button::builder()
+                .action_name("win.tab_append")
+                .icon_name("tab-new-symbolic")
+                .tooltip_text("New tab")
+                .build(),
+        }
+    }
+
+    // Getters
+    pub fn widget(&self) -> &Button {
+        &self.widget
+    }
+}