use bootstrap sass css
added header and footer, devided into partials
using Sass variables and nesting in CSS
added routing variables and fixed links
simplified tests using support/utilities, before section and subject
User controller added with routing, html and test.
added tests and simplified them (DRY)
refactored tests for chapter 5
added User model with tests
added a secure password to user, with a few tests
add authentication test and ensure password has length >= 6
finished exercises of chapter 6