updated readme of each example with a screenshot/gif and more details about the example.

added more comments to code

simple_material_app/README.md

@@ -1,8 +1,10 @@
-# simple_material_app
+# Simple Material App
+
+A simple material app
+
+<img src="demo_img.jpg" height="600em" />
 
-A new Flutter project.
 
 ## Getting Started
 
-For help getting started with Flutter, view our online
-[documentation](http://flutter.io/).
+For help getting started with Flutter, view online [documentation](http://flutter.io/).

simple_material_app/lib/main.dart

@@ -13,7 +13,9 @@ void main() {
         ),
         // Body
         body: new Container(
+          // Center the content
           child: new Center(
+            // Add Text
             child: new Text("Hello World!"),
           ),
         ),