RedisScheduler无法使用

[code4craft]

0.7.0版本中对RedisScheduler做了重构，使用了jedis.sadd来直接进行去重。

但是sadd的javadoc如下：

Integer reply, specifically: 1 if the new element was added 0 if the element was already a member of the set

所以这里是用法反了，应该改为：

public boolean isDuplicate(Request request, Task task) {
        Jedis jedis = pool.getResource();
        try {
            return jedis.sadd(getSetKey(task), request.getUrl()) == 0;
        } finally {
            pool.returnResource(jedis);
        }
    }