Add Greeting Class for Hello World TDD demonstration

Personal/Test Driven Development/Hello World/src/main/java/hello/world/App.java

@@ -1,13 +0,0 @@
-package hello.world;
-
-/**
- * Hello world!
- *
- */
-public class App 
-{
-    public static void main( String[] args )
-    {
-        System.out.println("Hello World!");
-    }
-}

Personal/Test Driven Development/Hello World/src/main/java/hello/world/Greeting.java

@@ -11,7 +11,12 @@ public class Greeting {
         this.message = message;
     }
 
-    public String getMessage() { return message; }
-    public void setMessage(String message) { this.message = message; }
+    public String getMessage() {
+        return message;
+    }
+
+    public void setMessage(String message) {
+        this.message = message;
+    }
 
 }