moved CSS extraction into extractor to facilitate blocking operations
moved CSS extraction into extractor to facilitate blocking operations

mozilla-services/pageshot,mozilla-services/pageshot,fzzzy/pageshot,mozilla-services/screenshots,mozilla-services/screenshots,fzzzy/pageshot,fzzzy/pageshot,mozilla-services/screenshots,mozilla-services/screenshots,fzzzy/pageshot,mozilla-services/pageshot,mozilla-services/pageshot