* initial pushshift/rexport merge implementation, using id for merging
* smarter module deprecation warning using regex
* add `RedditBase` from promnesia
* `import_source` helper for gracefully handing mixin data sources
- modernize:
- add REQUIRES spec for pdfannots library
- config dataclass/config stub
- stats function
- absolute my.core imports in anticipation of splitting core
- use 'paths' instead of 'roots' (better reflects the semantics), use get_files
backward compatible via config migration
- properly run tests/mypy