title: Compact a comma delimited number list into ranges
body: <p>I'm looking for a clever way to do the following operation:</p>
  
  <p>Take a list of numbers:</p>
  
  <p>1, 2, 3, 4, 5, 12, 13, 14, 19</p>
  
  <p>and compact it into a string like so:</p>
  
  <p>1-5, 12-14, 19</p>
  
  <p>With the following rule: only compress into a range (i.e. use a dash) when the count of numbers in the range is 3 or more.</p>
  
  <p>I.e.: 1, 2, 4, 5 would result in: 1, 2, 4, 5 and NOT: 1-2, 4-5</p>