Update README.md

Author: ProgramFan

README.md

@@ -5,3 +5,11 @@ Docker builder for gitit
 This is adpated from [Gitit-Bigger](https://github.com/menduo/gitit-bigger). I
 changed the base image to debian testing (debian 9) so that gitit-0.12 is
 available.
+
+This image tries hard to be small and simple. It contains only gitit related
+tools and is intended to be used as a base image for real gitit applications.
+See
+[gitit-templates-enhanced](https://github.com/programfan/gitit-template-enhanced)
+for an example.
+
+`utils` contains some interesting utilities for solving integrating problems.