Wrap Embedded Iframe Videos

I am looking to find a way to wrap any embedded iframe videos in another div in order to make them responsive.

Here is an article explaining more on what I am attempting to do:

http://css-tricks.com/NetMag/FluidWidthVideo/Article-FluidWidthVideo.php

I would like to use the option to wrap the iframe in a videoWrapper div. Where in the code can I add this div around any embedded videos?