Add management command for converting a downloaded topoJSON world map into a smaller version that we can use. With instructions for how to download and convert the input file.
Update the map to use d3.js v5 and topoJSON
This means we can use a more detailed map (e.g. Mauritius is now visible) but the map file is much smaller (115KB vs 577KB).
This means we can use a more detailed map (e.g. Mauritius is now visible) but the map file is much smaller (115KB vs 577KB).
For #143