Hashes hkeys and hvals refactored to return a set instead of a list.

It looks like the order is not guaranted, so a set seems much adapted than a list.

src/main/java/redis/clients/jedis/BinaryShardedJedis.java

@@ -164,12 +164,12 @@ public class BinaryShardedJedis extends Sharded<Jedis, JedisShardInfo> implement
         return j.hlen(key);
     }
 
-    public List<byte[]> hkeys(byte[] key) {
+    public Set<byte[]> hkeys(byte[] key) {
         Jedis j = getShard(key);
         return j.hkeys(key);
     }
 
-    public List<byte[]> hvals(byte[] key) {
+    public Set<byte[]> hvals(byte[] key) {
         Jedis j = getShard(key);
         return j.hvals(key);
     }