title: aasm after callback with argument
body: <p>I'm using the <a href="https://github.com/aasm/aasm" rel="noreferrer">aasm</a> (formerly <code>acts_as_state_machine</code>) gem in my rails 4 application. I have something like this on my <code>Post</code> model</p>
  
  <pre><code>  ...
    aasm column: :state do
      state :pending_approval, initial: true
      state :active
      state :pending_removal
  
      event :accept_approval, :after =&gt; Proc.new { |user| binding.pry } do
        transitions from: :pending_approval, to: :active
      end
    end
    ...
  </code></pre>
  
  <p>When I call <code>@post.accept_approval!(:active, current_user)</code> and the after callback gets triggered, in my console I can inspect what <code>user</code> is (that was passed into the Proc) and it's <code>nil</code>! </p>
  
  <p>What's going on here? What is the correct way to call this transition?</p>