Create micropost model
Validate presence of user_id for micropost
Add associations between user and microposts.
Order microposts with most recent first.
Destroy associated microposts when their users are destroyed.
Validate presence and length of microposts.
Add microposts to appear in User#show
Complete display templates for microposts.
Add microposts controller; restrict access to actions on microposts to signed in users.
Add ability to create new microposts on the root_url for signed in users
Add proto-feed
Allow user to delete their microposts.