Exit child when supervisor vanished.

This can happen when the supervisor receive a `SIGKILL`. Since `SIGKILL`
can not be trapped, supervisor does not have the luxury to cleanup its
children.

So, each child polls on its supervisor every 60 seconds. In case the
supervisor does not respond, it will exit.

Signed-off-by: chatgris <jboyer@af83.com>
Bump version

Signed-off-by: chatgris <jboyer@af83.com>