sample_data.rake: modified content to be that of Hartl listing 11.17
routes.rb: modified content to be that of Hartl listing 11.18
static_pages_spec.rb: added 2 tests from Hartl listing 11.19
shared/_stats.h.e: created; added content of Hartl listing 11.20
static_pages/home.h.e: added content from Hartl listing 11.21
custom.css.scss: added content from Hartl listing 11.22
users/_follow_form.h.e: created; added content from Hartl listing 11.23
routes.rb: added :create, :destroy resources for :relationships
users/_follow.h.e: created; added content from Hartl listing 11.25
users/_unfollow.h.e: created; added content from Hartl listing 11.26
users/show.h.e: added content from Hartl listing 11.27
authentication_pages_spec.rb: added content from Hartl listing 11.28
user_pages_spec.rb: added content from Hartl listing 11.29
users_controller.rb: added 'following', 'followers' actions and modified :signed_in_user before_action
users/show_follow.h.e: created; added content from Hartl listing 11.31
user_pages_spec.rb: added 6 tests from Hartl listing 11.32
authentication_pages_spec.rb: added 2 tests from Hartl listing 11.33
relationships_controller.rb: created; added 'create', 'destroy' actions and :signed_in_user before_action
user_pages_spec.rb: fixed typo: 'sign_in user' instead of 'sign_in other_user'
authentication_pages_spec.rb: fixed typo: 'relationship_path(1)' rather than 'relationships_path(1)'