accessToken 过来的时候，保存 Session，以便 Turbolinks App 的表单可以提交

Author: huacnlee

app/controllers/application_controller.rb

@@ -102,7 +102,10 @@ def authenticate_user!(opts = {})
 
   def current_user
     if doorkeeper_token
+      return @current_user if defined? @current_user
       @current_user ||= User.find_by_id(doorkeeper_token.resource_owner_id)
+      sign_in @current_user
+      @current_user
     else
       super
     end