This was not working because the filename (and only the filename) was being added to the YAML front matter. I think this was probably a typo and is an easy fix.
While I was at it I added the ability to save tag information as well. I have it set to use the categories key by default for tags, but some people may want to actually import the information as tags instead. In that case, they can specify a specific key.
You did a great job with this and I'd very much like to see #402 accepted. This patch will fix a bug and add a tiny bit of functionality. If you accept and merge this it should automatically be included in #402.
YAML front matter fix, cleaned up slug generation, added tags and sto…
…re some posterous information from the original post.