Add the controller, route setting, html.erb, and test for Session(8.1.1).
Add tests for Sign in page(8.1.2).
Add Sign in form (8.1.3).
Add page redirecting in Sign in page, and flash message there including a bug (8.1.5).
Fixed probrem with sign in flash message (8.1.5).
Add the remember_token blank test and create_remember_token method (8.2.1).
Add cookies. (8.2.2)
Add cookie checking method 'current_user' (8.2.3).
Added sign in&out features. (8.2.4)
Add auto-sign-in feature when you signed up. (8.2.5)
Add sign out feature and start to try cucumber.
Finish sign in