Deprecating Sharded Jedis 

It's for completely removing ShardedJedis at 3.0.0.

Discussion for deprecating starts at https://groups.google.com/d/msg/jedis_redis/avphfQld81Y/X_uouHp_lCIJ.
Although it couldn't get many "agreement"s, but no "disagreement" received.
So we will start removing ShardedJedis.

@xetorthio @marcosnils Please review and comment! Thanks!