added omniauth facebook
added figaro to gemfile
updated application.yml
added omniauthable to user model
added omniauth routes
added FB signin link to landing page
added config to devise.rb
added omniauth callbacks controller
changed devise routes
updated omniauth controller
added from_omniauth method to user model
added username to users model
updated devise config
updated devise sign in form
added username attr_acc and validation
added username to user model
updated seed file with username
updated user model devise settings
added twitter sign in method
added twit sigin in link