Diff syntax highlighting in Github Markdown

Github’s markdown supports diff when formatting code. For example:

```diff
public class Hello1
{
   public static void Main()
   {
-      System.Console.WriteLine("Hello, World!");
+      System.Console.WriteLine("Rock all night long!");
   }
}
```

Output:

and it should give you the Diff looks you are looking for, highlighting in red what has been removed and in green what has been added.