use it both in my.fbmessenger and my.reddit if in the future any new modules need to be switched to namespace package structure with all.py it should make it easy to do related: - https://github.com/karlicoss/HPI/issues/12 - https://github.com/karlicoss/HPI/issues/89 - https://github.com/karlicoss/HPI/issues/102
* 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