Author: Jonathan Worthington <jn...@jnthn.net>
Date: 2015-06-06 (Sat, 06 Jun 2015)
Update design docs for how Str/NFG has worked out.
Of note, the StrLen and StrPos types are gone, and Str only works at
grapheme level; as per S15 we have Uni and its subtypes for working
at codepoint level, and Buf for working at bytes level.