title: An efficient way to find all SKNodes within a certain distance from a given point?
body: <p>If I want to know which node or nodes cover certain point of the scene I can do either <code>scene.nodeAtPoint(point)</code> or <code>scene.nodesAtPoint(point)</code>. Is there an efficient way to do something similar with a <em>circle</em>?  That is to be able to find all nodes that have their positions within certain distance from a given point.</p>
  
  <p>I need this to be able to handle user taps better.  The scene is rather scarce (not much user-active sprites on it), so there is no need to demand the user to be very precise with tapping.  I want to use some sort a tolerance around the coordinates of the tap and detect the node that is just close enough to tap location.</p>
  
  <p>The best idea that I have so far is to do <code>nodeAtPoint()</code> several times: at the location of the tap, and then at various offsets from it (e.g. up, up-right, rigth, ..., up-left).</p>