Merge pull request rust-lang#2649 from Kixunil/patch-1

Added an example of slicing result

Author: carols10cents

src/ch04-03-slices.md

@@ -281,6 +281,8 @@ to part of an array. We’d do so like this:
 let a = [1, 2, 3, 4, 5];
 
 let slice = &a[1..3];
+
+assert_eq!(slice, &[2, 3]);
 ```
 
 This slice has the type `&[i32]`. It works the same way as string slices do, by