Map builder

Yesterday I implemented a lib to load maps created with the tiled map editor. This should make making maps easy. So far it can render different layers but all of them under the character (maybe we should use a name convention to say which layers go over the character and which under).

I made a school tileset and map (download by clicking on "raw") out of
Kurai's background for testing.

The editor also supports "objects" on top of the map (just some rectangles) that we could use to put triggers like adding enemies at certain places, putting stuff like cakes and stuff like that.

It still needs some improvement, since there are lines showing between tiles, but it could be useful to start showing how things would look.

BTW, tiles can be as big as we want, so there shouldn't be a problem with the levels looking too "squared" or repetitive.