Made all events in analog_input.DaqClient private.
Made analog_input.DaqInterface.daq_program_path private.
Made default_port and default_host in analog_input private.
docstring fix
Added automatic conversion of printed debug information to str and data written on the socket to bytes to make analog_input more python version invariant.
Replaced all str.encode and bytes.decode with the python version invariant versions to become more python 2 compatible
Moved from using subprocess.check_output to subprocess.Popen for python 2 compatibility and handled the fact that Popen.communicate only supports a timeout for python >= 3.3