title: How do I group objects in a set by proximity?
body: <p>I have a set containing thousands of addresses.  If I can get the longitude and latitude of each address, how do I split the set into groups by proximity?</p>
  
  <p>Further, I may want to retry the 'clustering' according to different rules:</p>
  
  <ul>
  <li>N groups</li>
  <li>M addresses per group</li>
  <li>maximum distance between any address in a group</li>
  </ul>