Finish Sxn 9.2.2: Requiring right user

1.  Fixed bug for patch request in authentication_pages_spc - added code to
    describe block for `type: :request`, enabling Capybara to make requests
    from the spec/features folder.
2.  Changed code for `redirect_to(root_url)` to `redirect_to(root_path)` in
    the authentication_pages_spec file.  Former was specified in the tutorial
    but generated a Missing host to link to error.
3.  All tests passing green at this point, though with some minor deviations
    from the tutorial code.