Adds devise user model
refactor spec controller
Adds user authentication token
Adds sessions controller create action
Adds destroy session action added
Adds authenticable module to manage authentication methods
Adds authorization for users controllers
Adds user_signed_in ? method to know whether the user is logged in or not
Merge branch 'chapter5'
Chapter 5 authentication and authorization
Adds product model validation
Adds products create,update and destroy action nested on the user resources
Update test environment factory gems to work on development
Merge with origin