title: Iterate an array, n items at a time
body: <p>I have an array: </p>
  
  <pre><code>[1,2,3,4,5,6,7,8,9,0] 
  </code></pre>
  
  <p>that I'd like to iterate 3 at a time, which produces</p>
  
  <pre><code>1,2,3  and  4,5,6  and  7,8,9   and   0
  </code></pre>
  
  <p>What's the best way to do this in Ruby?</p>