Here memory leaks, the process will lead to the collapse of the long-running

test code:

    var i = 0;
    while(true){
        var buf = pb.Serialize(obj, 'ucloud.UMessage');
        if(!(++i % 10000)){
            console.info(i);
        }
    }
Merge pull request #16 from wentianle/master

Here memory leaks, the process will lead to the collapse of the long-run...