Add basic documentation

[timothymtorres]

I noticed the doc folder is gone. Not sure if that was intentional or not, but I think the project could benefit from some basic documentation. You should also include documentation for what properties a object/layer/map table contains. This will be useful for when people are creating (whatever kind of) objects to look at a table they can reference.

Ie.

    local fake_object_json_data = {
      gid = 1075,
      height = 32,
      width = 32,      
      name = "foo",
      rotation = 0,
      type = "blah",
      visible = true,
      x = 0, 
      y = 0,
      properties = {},
    }