issue #32

Added support for drawing tiles in object layers. When layer.properties.isSolid is set (custom properties in Tiled) the layer also supports collision, given the tiles have a collisionmap/objectgroup.
I am new to batches and I tried to use your existing code. I used a different technique to split into multiple batches. You split into batches according to the position of the tile. I had in mind that objects could move positions in the future.
I did not check the orientation since I do not understand what happends there. This could be a problem.