adding notebook-list, a list of notebooks to *include* in run-all-notebooks...

adding notebook-list, a list of notebooks to *include* in run-all-notebooks (already modified in last commit).  This is so you can run tox without it choking on your local broken notebooks in development :)

notebooks/notebook-list

+# list of notebooks to include in run-all-notebooks.py test
+Agent-Close-Following.ipynb
+flatland-animate.ipynb
+render-episode.ipynb
+Scene_Editor.ipynb
+simple_example1_env_from_tuple.ipynb
+simple_example2_generate_random_rail.ipynb
+simple_example_3_manual_control.ipynb
+Simple_Rendering_Demo.ipynb
+test-collision.ipynb
+test-saved-envs.ipynb