check headers

Сheck the headers in the request

We have a stray `console.warn()` but that is something that I need to clean up.

In theory in `stealthmode` Drakov should only log the items it needs to confirm that it has started up correctly.

We do this because we use Drakov to run scripted browser tests and having `stealthmode` makes our Jenkins build logs a lot easier to read. :)

An example of our implementation can be found in this project: https://github.com/Aconex/grunt-blueprint-test-runner