RESET

big time reset, we are not using TMX anymore, but instead using the JS 
format because it is way simpler to parse

tests/test_data/simple_external_tileset/tile_set.json

@@ -0,0 +1,14 @@
+{ "columns":8,
+ "image":"..\/images\/tmw_desert_spacing.png",
+ "imageheight":199,
+ "imagewidth":265,
+ "margin":1,
+ "name":"tile_set_image",
+ "spacing":1,
+ "tilecount":48,
+ "tiledversion":"1.3.1",
+ "tileheight":32,
+ "tilewidth":32,
+ "type":"tileset",
+ "version":1.2
+}