Note that `Capybara.app_host` now returns `nil` by default and that
breaks tests using `lvh.me` or our custom `app_host` method, so we're
setting `Capybara.app_host` to the value it had in earlier versions of
Rails. I also haven't found a way to remove the code to set the
integration session host in relationable tests which I mentioned in
commit ffc14e499.
Also note that we now filter more parameters, and that they match
regular expressions, so filtering `:passw` means we're filtering
`passwd`, `password`, ...
