refactor, structure to make updating easier

Love the idea; I have two of my own kids in BTV :)

A few updates to the structure I saw here, also based on the concept poster:

1.) Restructured index.html to be easier to navigate - all the geodata is now called from separate files
2.) Added bootstrap for easy styling and functionality
3.) Made the Childcare centers modular - i.e. they're now being called to the map from childcare-centers.geojson, which can be easily [added to here](http://geojson.io/#id=gist:wboykinm/2f592dd705c119a22f03&map=14/44.4749/-73.2117). Once new features have been added/edited, just copy the new JSON back into childcare-centers.geojson and the map will update

It's a bit more work than I can handle right now to add the ward-level stats layers, mostly because it requires some preliminary GIS. Good luck with that part of it, and with building up the app!