title: How to sort an RDD and limit in Spark?
body: <p>I have RDD of Foo class : <code>class Foo( name : String, createDate : Date )</code>.
  I want an other RDD with 10 percent older <code>Foo</code>.
  My first idea was to sort by <code>createDate</code> and limit by 0.1*count, but there is no limit function.</p>
  
  <p>Have you an idea?</p>