Add Sessions Controller and resources with Integration test
Add the tests for signin success and failure
Gemfile add hirb
Code for the signin form
A preliminary version of the Sessions create action.
An (unsuccessful) attempt at handling failed signin.
Correct tests for signin failure.
Correct code for failed signin.
The completed Sessions controller create action（not yet working）.
Including the Sessions helper module into the Application controller.
A first test for the remember token.
$ rails generate migration add_remember_token_to_users
A migration to add a remember_token to the users table.
$ bundle exec rake db:migrate
$ bundle exec annotate --position before
A test for a valid（nonblank）remember token.
[Add] A before_save callback to create remember_token.
[Add] The complete（but not-yet-working）sign_in function.
[Add] Defining assignment to current_user.
[Add] Finding the current user using the remember_token.