Added method of logging HTML output from WebDriver along with screenshot of page

Sorry, new to this whole making patches thing, but this is my suggestion for saving the HTML of the page along with a screenshot. Sometimes a screenshot is not enough, and it's really useful to see, when a fail occurs, what the HTML was doing, so this achieves it.

I have screwed the patch up a bit and I'm not sure how to fix it but you can see where I was going with it.