Optimise page library downloads

[chatch]

The pages are pretty fat. Look at ways of optimising the page download size. Especially for mobile. Some possible optimizations:

• aggregate into a single file (use gulp or something)
• leaflet mapping - use static maps where it makes sense and reduce the tile sizes - see tile.osm.org downloads; is it possible to get a subset of leaflet functionality? the library is big
• bootstrap - already using a subset but we're only using it for grid and popups - replace with small specific libs or do the grids with our own css

what else?