added functionality (use names), updated regex
added functionality (use names), updated regex

added argument -n, --use-names
urls that have a name at the end like "https://boards.4chan.org/wsg/thread/7813282/ylyl-gifs" will use this name instead of the thread id - the script will store the images to downloads/wsg/ylyl-gifs instead of downloads/wsg/7813282
in case you downloaded some images already with this argument and forget to add it the next time you run the script, the script will notice that and use the name anyway

4chan seems to use another url for their pictures now, therefore I updated the regex in line 48 (line 42 before)
Exceen/4chan-downloader