Finalise stats map

[pospi]

Mainly a wishlist, will probably only get the first one done for launch.

• [x] Link stats counters to the map shading when hovered (both intensity and colour)
• [ ] Show tweets on the map as they occur (design pending)
• [ ] Show senator events on the map somehow (design pending - suggest just flashing a random ward within the state?)
• [ ] Implement ward hovering on stats map with infotips for actions taken (maybe. Also - what to do with senators?)
• [ ] Some UI to toggle map pan/zoom interaction