jsonp buffered loader

bufferedLoader = function (eleLoaded, loader, callback) {
    	/*
    	1. eleLoaded (index)
    	2. loader (start, end)
    	HELP: the loader's callback func will enrich store, and unless passes the checking of bufferedLoader,
    	it will recursively call the bufferedLoader. e.g. loaderCallback (data) { ... fn(i, end) }
    	NOTE: if there is somehow a terminating condition, you can place it in the loader/loaderCallback, and 
    	manually excute the callback func above.
    	3. callback - when all of the data is ready

        1. eleLoaded (index) 判断每个数据是不是已经加载到了
        2. loader (start, end) 迭代加载尚未加载的数据，当有一部分数据还没有加载的话
        3. callback () 当所有需要的数据都已经加载到了，才会执行要执行的操作
    	 */
    	var fn = function (start, end) {
			for (var i = start; i < end; i++) {
				if (!eleLoaded(i)) {
					loader(i, end);
					return;
				}
			}
			callback();  		
    	};
    	return fn;
    };