title: NSPredicate with boolean is not comparing a boolean to NO
body: <p>I'm using CoreData and my entity has a boolean property called "isReward".</p>
  
  <p>I'm trying to fetch the entity and filter out all results where isReward == YES. </p>
  
  <p><code>isReward != YES</code> does not work. </p>
  
  <p><code>isReward == NO</code> does not work. </p>
  
  <p><code>NSPredicate predicateWithFormat:"isReward != %@", [NSNumber numberWithBool:YES]]</code> does not work</p>
  
  <p><code>isReward == Nil</code> works.</p>
  
  <p>What gives?</p>