Override `querystring.escape` only locally

In my opinion, Node’s global `querystring.escape` is just poor API design.
Since Node modules are cached in memory, overwriting `querystring.escape` will
overwrite it for every other client of that module which can lead to subtle,
hard to find bugs. In my case, HTML emails using `querystring.stringify` to
escape query string parameters started being truncated due to unescaped `&`
once I added `node-parse-api` as a dependency.

Workaround: Overwrite `querystring.escape`, use `querystring.stringify`, and
then restore `querystring.escape` to original implementation.

I filed a bug against Node.js core here:
https://github.com/joyent/node/issues/8672
Merge pull request #16 from FiftyThree/master

Override `querystring.escape` only locally