* Add a rough prototype allowing a developer to pre-download data sources for all ETLs
* Update code to be more production-ish
* Move fetch to Extract part of ETL
* Create a downloader to house all downloading operations
* Remove unnecessary "name" in data source
* Format source files with black
* Fix issues from pylint and get the tests working with the new folder structure
* Clean up files with black
* Fix unzip test
* Add caching notes to README
* Fix tests (linting and case sensitivity bug)
* Address PR comments and add API keys for census where missing
* Merging comparator changes from main into this branch for the sake of the PR
* Add note on using cache (-u) during pipeline
