title: Does a Rails helper exist for "one, two, and three"?
body: <p>Sorry for such a trivial question, but I'd feel silly building this if it already existed.</p>
  
  <p>I have a vague memory of there being a Rails helper that could turn <code>['one', 'two', 'three']</code> into "one, two, and three", but I could be totally making things up. And I can't quite figure out where in the API to look since it's not in the TextHelper module, nor can I figure out what to search for.</p>
  
  <p>Does this method exist, or am I just imagining it?</p>