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/BinaryJedisCommands.java

@@ -60,9 +60,9 @@ public interface BinaryJedisCommands {
 
     Integer hlen(byte[] key);
 
-    List<byte[]> hkeys(byte[] key);
+    Set<byte[]> hkeys(byte[] key);
 
-    List<byte[]> hvals(byte[] key);
+    Set<byte[]> hvals(byte[] key);
 
     Map<byte[], byte[]> hgetAll(byte[] key);