title: Even numbers a list?
body: <p>How do I create a list and only extract or search out the even numbers in that list? </p>
  
  <p>Create a function <code>even_only(l)</code> that takes a list of integers as its only argument. The
  function will return a new list containing all (and only) the elements of l which are evenly divisible by 2. The original list l shall remain unchanged.</p>
  
  <p>For examples, <code>even_only([1, 3, 6, 10, 15, 21, 28])</code> should return <code>[6, 10, 28]</code>, and
  <code>even_only([1, 4, 9, 16, 25])</code> should return <code>[4, 16]</code>.</p>
  
  <p>Hint: Start by creating an empty list, and whenever you encounter an even number in it, add it to your list, then at the end, return your list.</p>