Issue #170: Transform path, not url (which will contain the querystring)...

Fixes #170 

@rcrichton if you could please review?

Seems [this](https://github.com/jembi/openhim-core-js/blob/47303baa5c8823df4753f6b1d36e376746f3fc8e/test/unit/routerTest.coffee#L205) test should've picked it up, but url was set without the querystring (whereas Koa sets it up with).