title: Behavior of shuffle on Set vs List using scala.util.Random
body: <pre><code> scala&gt; Random.shuffle((1 to 10).toSet)
   res10: scala.collection.immutable.Set[Int] = Set(5, 10, 1, 6, 9, 2, 7, 3, 8, 4)
  
   scala&gt; Random.shuffle((1 to 10).toSet)
   res11: scala.collection.immutable.Set[Int] = Set(5, 10, 1, 6, 9, 2, 7, 3, 8, 4)
  
   scala&gt; Random.shuffle((1 to 10).toSet)
   res12: scala.collection.immutable.Set[Int] = Set(5, 10, 1, 6, 9, 2, 7, 3, 8, 4)
  
   scala&gt; Random.shuffle((1 to 10).toList)
   res13: List[Int] = List(3, 9, 8, 5, 7, 6, 10, 2, 1, 4)
  
   scala&gt; Random.shuffle((1 to 10).toList)
   res14: List[Int] = List(5, 10, 2, 9, 4, 7, 8, 6, 1, 3)
  
   scala&gt; Random.shuffle((1 to 10).toList)
   res15: List[Int] = List(5, 9, 10, 6, 8, 3, 4, 1, 7, 2)
  </code></pre>
  
  <p>So shuffle can handle Lists just fine, but not sets ?
  Can't sets be shuffled ? 
  Why is res10 == res11 == res12 ?</p>