Use platform-aware UI library for native look and feel

- Added score layout

lib/score.dart

@@ -0,0 +1,25 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_platform_widgets/flutter_platform_widgets.dart';
+
+class Score extends StatelessWidget {
+  @override
+  Widget build(BuildContext context) {
+    return Row(
+      mainAxisAlignment: MainAxisAlignment.center,
+      children: <Widget>[
+        PlatformButton(
+          child: PlatformText("Start Over"),
+          onPressed: () {},
+        ),
+        PlatformText("Score:"),
+        PlatformText("999"),
+        PlatformText("Round:"),
+        PlatformText("999"),
+        PlatformButton(
+          child: PlatformText("Info"),
+          onPressed: () {},
+        )
+      ],
+    );
+  }
+}