Add exercise data exploration notebooks

notebooks.json

@@ -2,6 +2,8 @@
   "baseUrl": "https://github.com/INRIA/scikit-learn-mooc/raw/master/",
   "notebooks": [
     "notebooks/01_tabular_data_exploration.ipynb",
+    "notebooks/01_tabular_data_exploration_ex_01.ipynb",
+	  "notebooks/01_tabular_data_exploration_sol_01.ipynb",
     "notebooks/02_numerical_pipeline_ex_01.ipynb",
     "notebooks/02_numerical_pipeline_hands_on.ipynb",
     "notebooks/02_numerical_pipeline_introduction.ipynb",