added facebook_login_sdk
removed nickname and password_digest from users model
added facebook_auth data to users model
added user.create_with_omniauth method
modified sessoin creation method to use facebook authentication
added omniauth-facebook routes
added omniauth and omniauth-facebook to gemfile
added font-awesome; modified index_page_modal to use facebook login
added facebook app id to fb_login_sdk; added css for facebook login button
added omniauth.rb initializer
minor change to css for facebook button
made change to styling of facebook login
refactored user authentication logic into user.rb; added user profile photo on home page
Merge branch 'facebook-login'