Add pandas materials

[koudyk]

• Update attribution to include https://swcarpentry.github.io/python-novice-gapminder/07-reading-tabular.html
• Update module objectives
• 2.3_tabular-data-pandas.md
  • fill in pandas module from another SWC lesson
  • adapt dataset
  • in-code dataset paths
  • in-code data-specific details
  • in-code figure paths
  • code-created figures
  • illustrative figure contents
  • figure names
  • in-text figure paths
  • in-text dataset mentions
  • in-text dataset description
• 2.4_visualization.md
  • show visualizing with pandas
  • adapt dataset
  • in-code dataset paths
  • in-code data-specific details
  • in-code figure paths
  • code-created figures
  • illustrative figure contents
  • figure names
  • in-text figure paths
  • in-text dataset mentions
  • in-text dataset description