Use per-stage README instead of a "Detailed Outline"

Author: siddhantwahal

stage3.0_first_views/README.md

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+Stage 3 of the application adds a GUI using a simple TraitsUI view:
+    - Invoking `configure_traits` on the `ImageFile` model creates a simple
+    view.
+    - Separately, a matplotlib window reports detected faces.

stage3.1_first_views/README.md

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+Building on Stage 3.0, this version:
+- Adds a dedicated model-view for the `ImageFile` model.
+- Uses the `MplFigureEditor` to embed the matplotlib figure inside the
+  TraitsUI view.