Update _tools.responsive.scss

I really like inuit but it doesn't seem like there is a built in option to support older browsers with no media query support. I stole this technique from Ben @ Sparkbox - http://seesparkbox.com/foundry/structuring_and_serving_styles_for_older_browsers - would be cool if there was an option to check $serve-to-nomq-max-width too but I don't have the time to work that out just yet. See what you think, I just tried it on my project and it worked fine.