Add detailed outline to README

Author: siddhantwahal

README.md

@@ -84,6 +84,20 @@ are able to reach the end goal.
   - step 7: pyface application: background run with traits-futures [OPTIONAL]
   - step 8: 1-click installer
 
+### Detailed outline:
+
+- Stage 2:
+    - 2.0: Introduces a model class to represent image files and operations on
+      them.
+- Stage 3:
+    - 3.0: Introduces GUIs using a simple TraitsUI view
+        - A simple view is constructed by invoking `configure_traits` on the
+          `ImageFile` model.
+        - Separately, a matplotlib window reports detected faces.
+    - 3.1: 
+        - Adds a dedicated model-view for the `ImageFile` model
+        - Uses the `MplFigureEditor` to embed the matplotlib figure inside the
+          TraitsUI view.
 
 ## Contributing
 ### Code structure