Fix issue flagged by brakeman

  Confidence: High
  Category: Cross-Site Request Forgery
  Check: ForgerySetting
  Message: 'protect_from_forgery' should be called in Kracken::SessionsController
  File: app/controllers/kracken/sessions_controller.rb
  Line: 4

Per the suggestion we set it to raise an exception. If apps want to
override this in the subclasses they can change it there.

Author: cupakromer

app/controllers/kracken/sessions_controller.rb

@@ -2,6 +2,7 @@
 
 module Kracken
   class SessionsController < ActionController::Base
+    protect_from_forgery with: :exception
 
     def create
       @user = user_class.find_or_create_from_auth_hash(auth_hash)