Incorrect "delete" links

They include an extra path to the file as part of the "base url".

For example, the `(delete)` link for `wikidata/dir1/dir2/test.txt`
comes out as `http://localhost:5001/dir1/dir2/_delete/dir1/dir2/test.txt`.
I think it should be `http://localhost:5001/_delete/dir1/dir2/test.txt` instead.

I looked at `fileListToHtml` in `Network/Gitit/Handlers.hs` and it seems to do the right thing: `href $ base' ++ "_delete" ++ urlForPage (prefix ++ f)`

So the issue must be upstream of that, maybe in `getWikiBase`?

EDIT: I'm using the latest master from github.