add Sessions controller
add test cases for authentication page
add routes for signin/out pages
initialization of session
add test cases for authentication_pages
modified signin page
add test case of alert info signin with invalid info
action create with invalid info
add remember token to users
modified flash
include SessionHelper module
add test cases for remember token
add method create_remember_token
annotated user
persistent session accomplished with remember token
add sign_in?
header changes after signin/signout
add js of Bootstrap
add test cases after saving the user
auto signin after signing up