Feature/ipc

use a unix socket instead of a temportay file to signal activity

This change replace the use of a temportary file by a socket pair to
notify the master that the worker is still alive.

before we were doing the following:
- create a tmp file / worker
- write to it
- check the last update bey using os.stat

now:

- open a socket pair
- write to it
- on socket read we update the worker state