Get data on existing generators for Illinois in each zone

[samgdotson]

This issue may be closed when there is a pull request that adds a script and/or notebook that

• [x] downloads data on existing generators in Illinois from EIA
• [x] identifies the existing generators for each zone
  • [x] PJM
  • [x] MISO
• [ ] adds the csv data files (if they're small enough)

This data should be collected using EIA's API or gridstatus (if available).