MIGRATE: pandas_panel lecture from stats (#310)

* MIGRATE: pandas_panel lecture from stats

* migrate pandas_panel data

* update link to pandas lecture

* enable intersphinx

* remove intersphinx as not required in this series

* fix deprecation notices and minor review

Author: mmcky

lectures/_static/lecture_specific/pandas_panel/countries.csv

@@ -21,6 +21,7 @@ parts:
   - file: matplotlib
   - file: scipy
   - file: pandas
+  - file: pandas_panel
   - file: sympy
 - caption: High Performance Computing
   numbered: true