Committee refinement

This incorporates the helpful feedback of @theresaanna 

Mostly, this version reduces nesting. It has no `properties` dict and shows the newest record for every attribute on the top level. 

There was one name change, in Committees, the `election_year` for a candidate became `election_years`. It is now a list of years the committee was associated with a candidate rather than listing the candidate multiple times. 

This will close #171