refactor: rename motion_file to motions_file
refactor: start moving to a Stancer class
refactor: Stancer should load the Issues too
refactor: move Stance instantiation into Stancer
refactor: move issue_stance
refactor: Stancer.all_stances
refactor: 'grouping' option
feature: script to generate per-Issue stances
feature: exclusions
feature: read from URL as well as file

Mostly still WIP
refactor: Options object

We’re going to add more complex logic here, so split it out.
refactor: No need to store so much in scored_votes
refactor: split grouping votes from weighting them

as as step towards getting the data from different sources.
refactor: DataSources