[slideshare] improve metadata; flake8

- added 'views' and 'published' keywords
- fixed longer titles and descriptions

test/test_extractors.py

@@ -82,6 +82,8 @@ skip = [
     "exhentai", "kissmanga", "mangafox", "dynastyscans", "nijie",
     "archivedmoe", "archiveofsins", "thebarchive",
     # temporary issues
+    "mangareader",
+    "mangapanda",
 ]
 # enable selective testing for direct calls
 if __name__ == '__main__' and len(sys.argv) > 1: