Parsed URL was sometimes empty (in case of woff2 only fonts) - skip such rules.
More general regex for cleaning CSS.
Changed extension from .styl to .css.
Prevent downloading a file multiple times.
Added support for defining subsets.
Do not clean CSS in the downloaded file.
Do not ignore .woff2 font files.
The option fontBaseDir now specifies the relative path from the CSS file to the font file (instead of a prefix of the fontDestination that should be removed).