adding postgis and council geojson

[mattyweb]

Fixes #909

Adding PostGIS support
Adding council GeoJSON and endpoint (/geojson) for client

[mattyweb]

I need to add some tests.
And probably rename some stuff.

[jafow]

Looking good to me. I do not have enough context I think to be generally helpful but I think the setup here is 👌👌

[adamkendis]

Looks good to me. Only thing I noticed was that some of the precision on the coordinates has been lost, but I really don't know if we even need something like 14-16 decimal places on lat/lng. Couple comparison snippets below. Not sure if that's caused by casting geometry to string or something else. We can put it on dev and see how it looks in the client.

seeds/nc-boundary-geojson.json
nc_id: 6

"coordinates": [
  [
    [
      [
          -118.45005171864273,
          34.249915100597775
      ],
      [
          -118.45055441819916,
          34.2506346000586
      ],
      [
          -118.451585617486,
          34.2516467005137
      ],

sample json response you sent in slack
nc_id: 6

"coordinates": [
  [
    [
      [
        -118.450051719,
        34.249915101
      ],
      [
        -118.450554418,
        34.2506346
      ],
      [
        -118.451585617,
        34.251646701
      ],

[mattyweb]

per discussion on Slack, i think we're OK with losing some precision here (I think it was false accuracy).

i've also decided to push a separate PR to add some tests...there's some other stuff i want to refactor there anyway.