Reporter fail exception fix

This is a small fix for the runner.fail method that can fail with a WebDriverTimeoutException.

Tested with a misbehaving website that sometimes aborted requests (crappy firewall). In the case of a misbehaving/stuck page the test would fail (after various timeouts) but the webdriver would still be stuck and the subsequent screenshot request would fail. Tested with the firefox webdriver.

Also added support for configuration of the screenshot path.