I find this useful for quickly prototyping new levels in web based games,
instead of having to re-export to .png constantly.
Setup
Place all .tmx map files in the /maps directory. The
development server will serve these as static assets. Given any file
/maps/my_map.tmx, requests for /maps/my_map.png will return
the proper .png encoding of that map file. Ensure that the Accept
header in these cases is set to image/png.