add additional datasets

[mfherman]

• community district acs estimates
• city council
• school districts
• police precincts
• us congressional districts
• election districts

[vronizor]

Hi! Thanks for the great package :)

I know you haven't updated it recently, but for future reference: could be nice to also add United Hospital Fund Boundaries. They are the basic unit of geospatial health data in NYC. More info on this page.

I might take a stab at a PR in a few months when have time...