title: Sidekiq 3.4.2 and Rails 4.2.0 having error with 'undefined method perform_at'
body: <p>I have jobs class for ex</p>
  
  <pre><code>class TempJob &lt; ActiveJob::Base
      queue_as :default # To Do Design Queue
  
      around_perform do |job, block|
          puts "Before Perform'
  
          block.call
  
          puts "After Perform"
      end
  
      def perform(*args)
          puts "Job Start"
      end
  end
  </code></pre>
  
  <p>I am trying to schedule job to be execute 1hours from now</p>
  
  <pre><code>TempJob.perform_at(1.hour.from_now)
  </code></pre>
  
  <p>but it is giving me following error</p>
  
  <pre><code>NoMethodError: undefined method `perform_at' for TempJob:Class
  </code></pre>
  
  <p>Using Rails 4.2.0, Ruby 2.2.0, and Sidekiq 3.4.2.</p>