refactored: using_tabs example

using_tabs/lib/tabs/third.dart

@@ -0,0 +1,23 @@
+import 'package:flutter/material.dart';
+
+class Third extends StatelessWidget {
+  @override
+  Widget build(BuildContext context) {
+    return new Container(
+      child: new Center(
+        child: new Column(
+          // center the children
+          mainAxisAlignment: MainAxisAlignment.center,
+          children: <Widget>[
+            new Icon(
+              Icons.airport_shuttle,
+              size: 160.0,
+              color: Colors.blue,
+            ),
+            new Text("Third Tab")
+          ],
+        ),
+      ),
+    );
+  }
+}