create relationships model for following-users.
create relationships_controller.rb.
show followed/follower count in user/show.html.erb.
create action to show following/follower action in users_controller.rb
modify show_follow.html.erb to show following/follower users.
create follow/unfollow form in users#show.html.erb
show feed in users#show.html.erb when user is current_user.