Cannot properly display Japanese vertical text

[gotson]

It seems there's some issues with Japanese vertical text:

1. the pages are not wrapping properly, instead a single page is shown, instead of wrapping the text that overflows at the bottom.
2. the <spine page-progression-direction="rtl" > seems to be ignored, and the buttons / navigation is still left-to-right.

Here is a sample book:

japanese vertical.epub.zip

[gotson]

I suppose this is the actual problem: readium/css#141

meaning vertical writing will not get support anytime soon.