title: Box2d elastic rope joint
body: <p>I'm writing a game, and I need to make up a rope. I maked it by b2RopeJoint, but there I have not found an opportunity to make it elastic.
  Then I looked for b2DistanceJoint, everything is cool with the elasticity, but I can't find an ability to set a limit only to the maximum distance (without minimum one).</p>
  
  <p>How can I do it?</p>