Add min-height for iframe
Don't use stylesheet_link_tags

There attachments will be cached, so we don't want timestamped references to stylesheets.
Add viewport to head when using responsive styles.
Set height for IE7, don't use min-height for small devices.

IE7 doesn't implement min-height, so force the iframe height. We don't
want to set min-height for mobile as it's just a workaround for
desktop browsers setting a too-small height.
Try a smaller min-height for smaller devices.