migrate relationships table
Establish Relationship model validations
Establish passive relationships
migrate seed for following
_stats for home view
follow button
Follow/unfollow button
place stats and follow form in show view
show_follow view
integration test for following
generate RelationshipsController
#create and #destroy for RelationshipsController
code respond_to in RelationshipsController
allow follow/unfollow via Ajax
test feed
Micropost#from_users_followed_by
Finish ch12 with bugs