[trivial] PyZio: remove object class from inherit

Signed-off-by: Federico Vaga <federico.vaga@gmail.com>
[python] ZioUtil.py: remove deprecated string

Signed-off-by: Federico Vaga <federico.vaga@gmail.com>
[API] ZioInterface.py: define the interface API

Signed-off-by: Federico Vaga <federico.vaga@gmail.com>
[API] ZioCharDevice: comply with ZioInterface API

Signed-off-by: Federico Vaga <federico.vaga@gmail.com>
[feature] ZioCharDevice: remove unpack object option

Signed-off-by: Federico Vaga <federico.vaga@gmail.com>
[feature] ZioCharDevice: add unpack optional parameter

Signed-off-by: Federico Vaga <federico.vaga@gmail.com>
[feature] ZioCharDevice.py: add select() capabilities

Signed-off-by: Federico Vaga <federico.vaga@gmail.com>
[feature] ZioCharDevice.py: add is_device_ready() function

The function return True or False depending on device availability. It
uses the select() function to check if device is ready or not.

Signed-off-by: Federico Vaga <federico.vaga@gmail.com>
[feature] ZioObject.py: enable and disable can do the opposite job
[feature] ZioCharDevice.py: remove write support because untested
[doc] ZioAttribute.py: Improve documentation comment
[API] ZioInterface.py: add unpack data method

Signed-off-by: Federico Vaga <federico.vaga@gmail.com>
[trivial] ZioInterface.py: zio_interface_path is a class attribute

Signed-off-by: Federico Vaga <federico.vaga@gmail.com>
[doc] README: update

Signed-off-by: Federico Vaga <federico.vaga@gmail.com>
[release] setup.py: alpha release 0.4a

Signed-off-by: Federico Vaga <federico.vaga@gmail.com>