Enhancements

[jovany-wang]

• [ ] Make dousi::Remote annotation around a method not only a method pointer: dousi::Remote(Echoer::echo)
• [x] Init() accepts the listening port or the connecting target address. #16
• [x] Pass custom-defined class as argument.
• [ ] Code style formater.
• [ ] Refine traits and TraitCalls.
• [ ] Remove class AbstractService.
• [ ] Return a DousiFuture<bool> for void return method on client side.
• [ ] Support arrow protocol to exchange large relation-data.
• [ ] Use codec as plugable so that we can use msgpack or other codec like protobuf.