Add more documentation.

(TcpBase): New class.  This contains most of the old Tcp class,
	except for the socket creating and connecting code.
(Tcp): Renamed to TcpBase.
(TcpClient): New class.
(TcpClient.__init__): New method.

exceptions.

	constructor call.

API.

(stty_init): Change default value to False instead of None.
(__use): New function.
(_inherit_stty): New function.
(_stty_init): New function.
(_spawn): New arguments: inherit_stty, stty_init.  Only inherit
	stty settings if stdin is a tty.  If an exception occurs in
	the child, transfer it to the parent as a
	remote_exception.Remote object.
(Spawn.__init__): New optional arguments: inherit_stty, stty_init.
(spawn2): Pass all arguments to the Spawn constructor.

(Remote): New class.
(Remote.__init__): New method.
(serialize): New function.
(re_raise): New function.

input from the serial port.

pipe.

	argument: use_stderr_pipe.
(Spawn.__init__): New optional argument: use_stderr_pipe.  Set the
	stderr attribute to an Expectable object that represents the
	stderr output from the subprocess it it is true.  Get rid of
	the __pty attribute, and renamed __child to __child_pid.
(Spawn.send): Use self.fileno() instead of self.__pty.
(Spawn.close): Ditto.  Close the stderr pipe if present.
(spawn2): New function.  A possibly easier API if you want to
	have the stderr output in a separate Expectable.

(Tcp): New class.
(Tcp.__init__): New method.
(Tcp.send): New method.
(Tcp.close): New method.