ADDED: Logo.

Motivation and considerations:

- A Scryer certainly needs a raven. Ravens are among the most
  intelligent animals on earth.
- When writing Prolog programs, a few strokes are often enough.
- Purple is the colour most associated with magic and royalty,
  indicating the almost surreal and pure features provided by Scryer,
  in the lineage of Marseille Prolog.
- The shape of the silhouette looks a bit like an "S" for "Scryer".
- A square which surrounds the image is traditionally associated with
  finishing a proof (square, Latin "quadratum", has the same starting
  letters as "quod erat demonstrandum").

I call this raven: *Cryer*. Cryer is an archaic spelling for "crier",
an officer who makes public announcements in a court of justice.
The Prolog top-level likewise makes announcements about what is true.

README.md

@@ -5,6 +5,8 @@ source industrial strength production environment that is also a
 testbed for bleeding edge research in logic and constraint
 programming, which is itself written in a high-level language.
 
+![Scryer Logo: Cryer](logo/scryer.png)
+
 ## Phase 1
 
 Produce an implementation of the Warren Abstract Machine in Rust, done