add devise, run install and move notice to app layout
add devise user model
add /sign_in and /sign_up routes
generate devise views, customize sign_up form
add custom names for columns, notices and alerts
nicer forms for sign_up, sign_in, account confirmation
show alert / notice only if there is text
add sign_out route
add devise confirmable module
display nice login form in the navbar
Merge branch 'authentication'

Use the Devise Gem to provide authentication for users.