Update README

Author: AngusGMorrison

README.md

@@ -1,3 +1,11 @@
-# hexarch
+![An illustration of a honeybee standing on top of hexagonal honeycomb](public/hexagonal-architecture-og.jpg)
 
-The complete code for "Master Hexagonal Architecture in Rust"
+The complete code
+for [_Master Hexagonal Architecture in Rust_](https://www.howtocodeit.com/articles/master-hexagonal-architecture-rust).
+
+This repo is divided into branches corresponding to different parts of the guide:
+
+* 1-very-bad-app: how not to build a Rust application.
+* 2-slightly-better-app: a distinct improvement that separates the repository from the HTTP handlers. Recommended for
+  apps without significant domain logic.
+* 3-simple-service: demonstrates the `Service` trait and provides a general-purpose template for hexagonal Rust apps.