title: Combine consecutive numbers into range tuples
body: <p>I have a list like</p>
  
  <pre><code>[38, 98, 110, 111, 112, 120, 121, 898]
  </code></pre>
  
  <p>How can I merge consecutive numbers into a pair representing a range?</p>
  
  <p>desired output:</p>
  
  <pre><code>['38',
   '98', 
   '110,112',
   '120,121',
   '898']
  </code></pre>