* Switch CloudflareService from HttpartyCache to Danbooru::Http.
* Purge cached urls from Cloudflare when a post is replaced and the md5
doesn't change. This happens when a corrupted image is replaced or
thumbnails are regenerated. Before we purged urls when a post was
expunged, which was unneeded because those urls can expire naturally.
It was also wrong because the subdomains were hardcoded, the urls used
http:// instead of https://, and we didn't account for tagged urls.
