Merge pull request #176 from gperdrizet/dev

Updates to lesson 22

Author: gperdrizet

notebooks/notebooks.yml

@@ -210,4 +210,6 @@ units:
           - name: "Demo"
             file: "Lesson_22_demo.ipynb"
           - name: "Activity"
-            file: "Lesson_22_activity.ipynb"
+            file: "Lesson_22_activity.ipynb"
+          - name: "Activity solution"
+            file: "Lesson_22_activity_solution.ipynb"