Created a ring of death as the outer world cells. (#191)

Fixes #179.

Author: MLanghof

src/asmcup/runtime/Cell.java

@@ -14,6 +14,11 @@ public Cell(World world, int cellX, int cellY) {
 		this.cellY = cellY;
 
 		Generator gen = new Generator(world, this);
+
+		if (cellX == 0 || cellY == 0 || cellX == World.CELL_COUNT || cellY == World.CELL_COUNT) {
+			gen.square(gen.same(TILE_HAZARD, 3), 0, 0, World.TILES_PER_CELL);
+			return;
+		}
 
 		gen.square(gen.variantRare(TILE_GROUND), 0, 0, World.TILES_PER_CELL);