Read value from slider

- Added To-do. (Was supposed to be added ages ago, but I had HDD issues)

Todo.md

@@ -0,0 +1,9 @@
+# To-do
+
+## Part 1
+
+- [x] Add "Hit me" button
+- [x] Show a pop-up when the user taps it
+- [x] Put game info on the screen
+- [x] Put slider on screen: 1 -> 100
+- [x] Read value of the slider

lib/main.dart

@@ -78,8 +78,8 @@ class _GamePageState extends State<GamePage> {
         context: context,
         builder: (BuildContext context) {
           return PlatformAlertDialog(
-            title: Text("Hello There."),
+            title: PlatformText("Hello There."),
-            content: Text("This is my first pop-up."),
+            content: PlatformText("The slider's value is ${_model.current}"),
             actions: <Widget>[okButton],
           );
         });