add site navigation
add sign up
use bootstrap
add css
Use Html shim and partial
add css for footer
use named route in RSpec
refector routes with named route
Use named routes in View
simplify RSpec case
add Users controller

$ rails generate controller Users new --no-test-framework

instead of Users controller generated by scaffold
generate case for user pages

$ rails generate integration_test user_pages
case for signup page
named routes for sign up
add title and h1 for sign up page
add url of sign up on home page
Merge branch 'filling_in_layout'