Integrate LeafletJS 1.0

[mjrouser]

Leaflet has a new version out in beta! http://leafletjs.com/2015/07/15/leaflet-1.0-beta1-released.html

It has lots of performance enhancements and upgrades, so it would be great to see if it can fit with our current setup.

[sonya]

I downloaded the current leaflet-1.0.0-b1 and dropped it directly in the project. There was one line I had to change to make it stop throwing errors.

On line 11 of censusLayer.js, change
L.Class.extend
to
L.Layer.extend

After this it looks pretty okay, at least superficially