I am trying to incorporate Devise, Omniauth, and Facebook into my Rails 4 application.

devise.rb

Devise.setup do |config|

  require "omniauth-facebook"
  config.omniauth :facebook, "186855861506807", "d35a2cab845ada8ff2036c6f7b3281cd"

  config.secret_key = '1a1e48f23c2756567caf48b37bd659a87f28fa18c8a9a5eb47d7b595e222c82b57787e66be3d51a515f7c8d43a2bbeb721a412830d6247ba144a32ad14755610'

  config.mailer_sender = 'please-change-me-at-config-initializers-devise@example.com'

  require 'devise/orm/active_record'

  config.case_insensitive_keys = [ :email ]

  config.strip_whitespace_keys = [ :email ]

  config.skip_session_storage = [:http_auth]

  config.stretches = Rails.env.test? ? 1 : 10

  config.reconfirmable = true

  config.reset_password_within = 6.hours

  config.sign_out_via = :delete

end

omniauth_callbacks_controller.rb

class OmniauthCallbacksController < Devise::OmniauthCallbacksController   
  def facebook     
     @user = User.find_for_facebook_oauth(request.env["omniauth.auth"], current_user)      
     if @user.persisted?       
      sign_in_and_redirect @user, :event => :authentication #this will throw if @user is not activated
      set_flash_message(:notice, :success, :kind => "Facebook") if is_navigational_format?
    else
      session["devise.facebook_data"] = request.env["omniauth.auth"]
      redirect_to new_user_registration_url
    end
  end
end

routes.rb

Stynyl::Application.routes.draw do  
  devise_for :admin_users, ActiveAdmin::Devise.config
  ActiveAdmin.routes(self)
  resources :things

  devise_for :users, :controllers => { :omniauth_callbacks => "omniauth_callbacks" }
  
  resources :users, only: [:show, :new, :create] do
    member do
      get :following, :followers
    end
  end
 
  resources :relationships, only: [:create, :destroy]
  
  get '/about', to: 'pages#about'
  get '/myfeed', to: 'pages#myfeed'
  root 'things#index'
end

user.rb

class User < ActiveRecord::Base
  # Include default devise modules. Others available are:
  # :confirmable, :lockable, :timeoutable and :omniauthable
  devise :database_authenticatable, :registerable, #:recoverable,
          :rememberable, :trackable, :validatable, :omniauthable

  has_many :things

  validates :name, presence: true, length: { minimum: 2, maximum: 20}
  validates :username, presence: true, length: { minimum: 2, maximum: 20}
  validates :username, uniqueness: true
  validates :email, presence: true
  validates :email, uniqueness: true

  

  has_attached_file :avatar, :styles => { :medium => "300x300>", :thumb => "100x100>" , :nav => "25x25"}

  extend FriendlyId
  friendly_id :username

  def show
    
  end

  #follow features
  has_many :followed_users, through: :relationships, source: :followed
  has_many :relationships, foreign_key: "follower_id", dependent: :destroy
  has_many :followed_users, through: :relationships, source: :followed

  def following?(other_user)
    relationships.find_by(followed_id: other_user.id)
  end

  def follow!(other_user)
    relationships.create!(followed_id: other_user.id)
  end

  def unfollow!(other_user)
    relationships.find_by(followed_id: other_user.id).destroy!
  end

  def feed
    Thing.from_users_followed_by(self)
  end

  has_many :reverse_relationships, foreign_key: "followed_id",
                                   class_name:  "Relationship",
                                   dependent:   :destroy
  has_many :followers, through: :reverse_relationships, source: :follower




  def self.find_for_facebook_oauth(auth, signed_in_resource=nil)
    user = User.where(:provider => auth.provider, :uid => auth.uid).first
    if user
      return user
    else
      registered_user = User.where(:email => auth.info.email).first
      if registered_user
        return registered_user
      else
        user = User.create(name:auth.extra.raw_info.name,
                            provider:auth.provider,
                            uid:auth.uid,
                            email:auth.info.email,
                            password:Devise.friendly_token[0,20],
                          )
      end    
    end
  end
end