Version 0.04, first public release

 - self-edges expose a bug in dot, causeing no graph to be output
 - some hashes and arrays have a "shadow" on one edge, also a dot
   bug
 - "empty" cells have to be filled with a non-blank character, or
   dot draws them as zero-width cells (dot bug)
 - references to array and hash elements are not detected; they look
   like plain of scalar references
