Chapter 4.1 - Helpers
Chapter 5 - Layouts
Adding header and footer partials
using nesting and variables in CSS
I think nesting and variables are overkill for CSS; maybe not for JS
Section 5.3. Optimised routes, tests; use of _layouts
Addition of a user controller with User pages, rspec and routes
Modified rspec testing for User
Chapter 5: Finish layout and routes