This implements the first half of #39 (and a little bit of the second half).
👉 The JavaScript here is purposely written in highly browser-compatible ES5, to allow users to modify the code without having to set up a transpilation/module bundling toolchain. It uses Mithril.js for DOM/UI management and Leaflet.js 1.0.0rc1 for the map component.
👉 Aside from the UI flavor text, all of the action is done over the GeoReportv2 JSON API.
This implements the first half of #39 (and a little bit of the second half).