These comments are already present under the parse blocks, so the huge walls of text before the code are not needed anymore.
#basename
#filename
#file_ext
Add `#basename`, `#filename`, and `#file_ext` utility methods to Danbooru::URL and change a few places to use them. Simplifies parsing filenames in source URLs in various places.
Also fix it so that for adult works, we get the images posted by the artist in the replies. Example: https://www.plurk.com/p/omc64y (nsfw).