title: Redefining Rails' methods
body: <p>The Rails method <code>Array#to_sentence</code> allows for the following:</p>
  
  <pre><code>['a', 'b', 'c'].to_sentence # gives: "a, b, and c"
  </code></pre>
  
  <p>I would like to extend this method to allow it to take a block, so that you can do something like the following (where people is an array of Person objects, which have the name attribute):</p>
  
  <pre><code>people.to_sentence { |person| person.name }
  # =&gt; "Bill, John, and Mark"
  </code></pre>
  
  <p>I don't have a problem with writing the extension method. But I can't work out where to put it. The Rails core extensions get loaded somewhere down in the depths of <code>ActiveSupport</code>. 
  My need is for a place where user-defined code is always loaded, and is pre-loaded (before any application code).</p>