* Only suggest the Danbooru tag with the same name if there is no
matching wiki other name. Example: if we have the Pixiv tag `Fate` and
the Danbooru tag `fate_(series)` with other name `fate`, suggest that,
not the Danbooru tag `fate`.
* Don't suggest tags that are empty or whose wiki is deleted.
* Only split tags on "/" if there are no other matches, and only for Pixiv.
* For Pixiv, only include traditional media tags in tag list, not digital media (Photoshop, SAI).
* Add some tests.