adding code for signin form
adding a preliminary version of the sessions create action
adding an unsuccesfully attempt at handling failed signin
correct tests for signin failure
correct code for failed signin
adding some features for session controller create action
including the sessions helper module into the application controller
a first tes for the remember token
creating a migration to add remember token to users
deleting the unrequired migration
creating a migration for remebering user
enabling a migration to add a remember_token to users table
a test for valid (nonblank) remember token
adding a before_create callback to create remember token
creating a signin function
defining assignment to current user
finding the current user using the remember_token
adding the signed_in? helper method
changing the layout links for signed-in users
adding the Bootstrap javascript library to application.js