title: Check if is an attribute is a valid DOM attribute
body: <p>I've noticed that if you take an element with jQuery you can change every attribute with the attr method. That's what supposed to do right?</p>
  
  <p>Well, it's right but what if you do:</p>
  
  <pre><code>$('p').attr('foo','bar');
  </code></pre>
  
  <p>If you inspect the element with Chrome Tools or Firebug you will see that, in fact, it has now an attribute called foo with the value of bar.</p>
  
  <p>Does anyone knows a way to do a previous check and avoid this? Can something go wrong if this happen?</p>