by slashrsm: Fix error with comment-wrapped esi tags when there are outside iframes on page.

iframes that pull content from other URLs can cause errors like this:

"Blocked a frame with origin "http://web1.dev.examiner.com" from accessing a frame with origin "http://www.facebook.com". The frame being accessed set "document.domain" to "facebook.com", but the frame requesting access did not. Both must set "document.domain" to the same value to allow access."

There is no point in looking for esi tags inside iframes anyway so let's exclude them.