Add Facebook login with Sorcery

The facebook key and secret defined in the sorcery config file are for
testing only and need to be changed and not committed to source when
app is ready to go live

app/models/authentication.rb

@@ -0,0 +1,3 @@
+class Authentication < ActiveRecord::Base
+  belongs_to :user
+end

app/models/user.rb

@@ -1,5 +1,7 @@
 class User < ActiveRecord::Base
-	authenticates_with_sorcery!
+	authenticates_with_sorcery! do |config|
+    config.authentications_class = Authentication
+  end
 
 	validates :password, presence: true, confirmation: true, length: { minimum: 3 }, unless: ("id?" || "password_confirmation?")
 	validates :password_confirmation, presence: true, unless: ("id?" || "password?")
@@ -16,5 +18,7 @@ class User < ActiveRecord::Base
 
 	has_many :user_organization_relationships
 	has_many :organizations, through: :user_organization_relationships
+  has_many :authentications, :dependent => :destroy
+  accepts_nested_attributes_for :authentications
 
 end