Allow testing non-catalog fonts

There are some fonts available from `fonts.googleapis.com/css?family=FAMILY` but not from `https://fonts.google.com/download?family=FAMILY` (which is only for font available from `https://fonts.google.com/specimen/FAMILY`)

GFR should be updated with an try/except or if/else so that when `download?family=FAMILY` fails it double checks `css?family=FAMILY&subset=ALL` using a blank user agent string in the HTTP GET request, to obtain the URLs of TTFs from `gstatic.com`