This reverts commit 2574fb3.
To conform to XHRs work in the browser, this change makes sure IO's node.js transport returns an empty string for falsy response bodies.
IE has a complex where it interprets falsy values into their string representations; e.g., `undefined` -> "undefined". This is clearly crazy so this combats the craziness by making sure IO sets XHR request bodies to an empty string.
Merge latest upstream dev-3.x into local branch.
…wsers handle regex the same.