title: rspec double('output').as_null_object still results in failures
body: <p>We upgraded to Rspec 2.14.5 and ruby 2.0.0p195.</p>
  
  <p>It appears the example in The Respec Book (page 53) that uses <code>double('output').as_null_object</code> as an approach to the failure due to multiple puts from the <code>game.start</code> method continues to fail.</p>
  
  <p>I think I have checked and rechecked the text I have typed in.  I have double checked to make the sure the prompt text is correct (the code with just the first text was working properly - now it fails because it sees the second puts).  Has there been a change in the <code>.as_null_object</code> specification?  Has this problem been seen by anyone else?</p>