refactored writing logic and added full stream supports CHANGES: - feat(connection): added `drain` event supports. - feat(connection): added `maxMessageSize` readonly property on connections. - feat(connection): now `createMessageWriter` method returns a `Writable` stream. - feat(connection): all `write` method supports `callback` parameter for draining. - feat(connection): refactored the writing logic. - fix(connection): close the connection correctly on received CLOSE opcode. - fix(encoding): simplified the code of encoder. - fix(encoding): failed to decode an empty FIN frame under SIMPLE mode. - fix(encoding): failed to decode an empty FIN frame under STANDARD mode. - fix(encoding): a message will be consume multiple times under STANDARD mode.