v0.2.0

Functionality:

• Checks raw_cache for existing parquet. If it exists, will not download
• Added keep_csv arg for download_raw_data
• Progress bar via tqdm for downloads
• Conversion of downloaded csvs to parquet, with some columns parsed as datetime or category

Other:

• More tests of code base
• Reorganise code base for better function reuse

Full Changelog: v0.1.0...v0.2.0