Fix for missing Host header

See http://stackoverflow.com/questions/17843968/how-do-manually-set-the-host-header-when-using-simplebrowser-webdriver-with-sele

I think a browser should automatically add a host header to eacht request. All major browsers do this. 

PS. I've not contributed much lately and I see other people enthusiastically joined in, so I'll not push this, but rather do a pull request. :)