Allow SSL callbacks from all providers

Fixes #99

Author: radar

app/controllers/spree/omniauth_callbacks_controller.rb

@@ -6,6 +6,7 @@ class Spree::OmniauthCallbacksController < Devise::OmniauthCallbacksController
   def self.provides_callback_for(*providers)
     providers.each do |provider|
       class_eval %Q{
+        ssl_allowed :#{provider}
         def #{provider}
           if request.env["omniauth.error"].present?
             flash[:error] = t("devise.omniauth_callbacks.failure", :kind => auth_hash['provider'], :reason => t(:user_was_not_valid))