Added Devise gem
rails g devise:install
Added a line in config/environments/development.rb
Added alert to application layout in addition to notice
rails g devise user
rake db:migrate
Added sign-up/sign-in/sign-out links to nav bar
Removing the need for a user to select themselves from a dropdown box when adding or updating a picture; instead, we use our knowledge of who is signed in to associate a picture to a user
DRYing up repeated controller code with a before_action filter