Fix tool_utils.resolve_path.
Fix tool_utils.resolve_path.

- return None if it can't recognize noto shorthand term or it's not present
- the remainder was being treated as an absolute path if it started with
  the directory separator, causing the prefix to be dropped.  Strip the
  head of the remainder while it looks like a separator.

googlei18n/nototools,anthrotype/nototools,moyogo/nototools,dougfelt/nototools,googlefonts/nototools,googlefonts/nototools,anthrotype/nototools,moyogo/nototools,googlefonts/nototools,dougfelt/nototools,googlefonts/nototools,googlefonts/nototools,anthrotype/nototools,googlei18n/nototools,dougfelt/nototools,moyogo/nototools,googlei18n/nototools