- define protocols.ClientHandler interface as base for client implementations
- implement protocols.ClientHandler in clientsim's ClientHandler type
- move protocol state handling into protocols.ServerProtocol and
protocols.ClientProtocol
- move protocolState type into protocols.go
- reduce clientsim's TestCommandGenerator responsibility to test command
generation
- rename protocols.Handler to ServerHandler
- rename ServerHandler methods to better express their purpose
- pass command and response as parameters
- simplify state machine and handle errors in serial/seriallink.go
- implement command read timeout
- remove currentCommand and currentResponse fields from MsgPackHandler
