Use qs.parse if parser undefined

[mushishi78]

It was failing to parse query strings in tests run on node. This change seems to make it work for me, perhaps it's what you had in mind with the original condition?

[lpinca]

I think that the intention is to provide the same API offered by the Node.js url module.
By default the query string is not parsed. You need to pass true or your own parser function in order to parse it.

var URL = require('url-parse');
var url = new URL('https://github.com/foo/bar?baz=qux', true);

[mushishi78]

Oh okay, well I was kinda skimming so I missed that.