Added header to application html template.
Finished section 5.1.1. Starting on 5.1.2 next, 'Bootstrap and custom CSS'.
Finished section 5.1.2
Completed initial CSS tutorial.  Next Section: 5.2, Sass and the asset pipeline.
Added OSX filesystem file to .gitignore.
Next section: 5.3.1
Next, 5.3.3: Named routes
Added header.
Next: 5.3.4
Next 5.4
Next: 5.4
Next: 5.4.2
Finished chapter 5.