Indent code in speaker notes (#476)

* Indent code in speaker notes

#475

* Update stack.md

* Update destructuring-arrays.md

* Update hashmap.md

* Update traits.md

src/traits.md

@@ -42,8 +42,7 @@ fn main() {
 * Types that implement a given trait may be of different sizes. This makes it impossible to have things like `Vec<Greet>` in the example above.
 * `dyn Greet` is a way to tell the compiler about a dynamically sized type that implements `Greet`.
 * In the example, `pets` holds Fat Pointers to objects that implement `Greet`. The Fat Pointer consists of two components, a pointer to the actual object and a pointer to the virtual method table for the `Greet` implementation of that particular object.
-
-Compare these outputs in the above example:
+* Compare these outputs in the above example:
      ```rust,ignore
          println!("{} {}", std::mem::size_of::<Dog>(), std::mem::size_of::<Cat>());
          println!("{} {}", std::mem::size_of::<&Dog>(), std::mem::size_of::<&Cat>());