Change Polygon to Marker.

Show total number of project on mouseover.
Change investment heatmap Polygons to Marker.
Add script to compute centroids for each Zone.

This script will be used to fill a new column
on locations table with the computed centroid.

It's also possible to identify Zones with invalid
data.
Merge pull request #12 from ecofunds/feature/change_poygon_to_marker

Feature/change poygon to marker