Rewrite binary operations implementation

 Previously binary data was stored as `new String(byteArray)` but it is not correct - as stated in String javadoc, it can replace unmappable characters.

As a result, when you save serialized java object it is not possible to deserialize it later.
@idyedov Ok, now charset is explicitly specified by . ```com.fiftyonred.mock_jedis.DataContainer#CHARSET```. Jedis always uses `UTF-8` - defined by ```redis.clients.jedis.Protocol#CHARSET```, so there is no need to override it.