Fix path-info parsing issues

* pathinfo callback functions should always return data if they handled
  the path.
* add cb_pathinfo function to tags plugin so it handles the path and
  sets the bl_type correctly.
Fix UnicodeEncodeError

(Might have been a UnicodeDecodeError--I forget which it was.)

Sometimes HTMLParser parses out a unicode for reasons I don't
understand. In this case, it was the title attribute of a lone link
tag. That caused the line to be a unicode and then suddenly everything
died at the ''.join(out).

This fixes that by making sure everything is a utf-8 encoded string.