Replaces calls to utils.pause with native node calls

Note that this may create some backwards incompatibility. It passes all tests but understand if further discussion is warranted.

This also closes #611 and potentially #644.

I see previous comments that req.pause was broken. Although there's some reference to updates as of 0.6.21 (http://blog.nodejs.org/2012/08/03/node-v0-6-21-maintenance/), further verification probably needed before accepting this pull request.