Included respond.js which comes with bootstrap

This was missing from _strap causing IE8 to force mobile views on desktop.
I've stopped using it since this episode on a project I was working on
https://twitter.com/francescolaffi/status/493711085804216320

jsdelivr includes, and is sponsored, by both (maxcdn and cdnjs), plus others.
It is more reliable by design http://www.jsdelivr.com/about.php