Moved Users#signed_in_user method to SessionsHelper.
Specs to ensure non-signed-in users cannot create or delete Microposts.
Create MicropostsController.
Write integration tests for Microposts pages.
Fleshing out MicropostsController.
Refactor error messages partial.
Provide form for creating new Micropost on home page if User signed in.
Create User#feed method, with preliminary implementation.
Implement Micropost feed with view on User home page.
Enable Microposts to be deleted by their User.