Create layout components

[adonyssantos]

The layout components will include:

1. <header>: Is the container for the navigation.
2. `: The nav menu.
3. <section>: Is a container (12 cols grid)
4. <main>: if is the only child of section will take the 12 columns
5. <aside>: there may be up to 2 and each one will take 3 column (to be taken away from <main>).