Map is sluggish on some devices

[jimsafley]

• The map tiles are slow to load, especially when zooming/panning.
• Geolocation is slow

I suspect the map gets slower the more markers are loaded onto it. According to alpha testers, the map runs very slow on the Mall wi-fi hotspots, but 4G works well (at least on iPhone).

We'll need to benchmark to see which components are slowing down the application. Use start() and stop() to benchmark.

Potential solutions:

• Use Leaflet.markercluster to minimize the amount of markers on the screen
• Use an item info panel instead of popups (#22), which will load item metadata on-demand instead of all at once.
• Compile the JavaScript using Closure Compiler
• Download OpenStreetMap tiles and serve locally (this is [strongly discouraged]())

[jimsafley]

The map behaves adequately after removing cluster animations in 3f4ec44053bdcae60061b7d73776cc760d03f981. Closing until field testing demonstrates this is a major problem.