Issue title: Turpentine @ responsive design sites
 Issue body: Hello,

Can i tell me how turpentine behaves at responsive design sites? A page seen in mobile is different from same page in desktop. How the cache operate in this case?
 Comments: 
 Comment 0: Have you read the documentation or even tested with a responsive theme? Please do it before asking any questions as most of the stuff is already there.
 Comment 1: This is really going to depend on how the responsiveness has been achieved. Usually, it involves font-end technologies like javascript and css media queries, which shouldn't be affected by using Varnish/Turpentine. When I test on the 1.9.x demo site (with responsive theme) I don't see any problems.
 Comment 2: Closing for lack of feedback.
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