Add user model and user validations (Ch. 6.2.5)
Add secure password to user attributes

http://ruby.railstutorial.org/chapters/modeling-users#sec-adding_a_secure_password 6.3-.1
Remove tracked .DS_Store and add to .gitignore
Finish 6.3.2, add secure password

http://ruby.railstutorial.org/chapters/modeling-users#sec-user_authentication
Finish secure password through 6.3.4

Next: http://www.railstutorial.org/book/modeling_users#sec-creating_a_user
Update gitignore to ignore Mac's .DS_Store files
Merge in modeling-users feature branch