Add a new module that allow users to configure hooks
on received ipc messages. The hook will execute the defined
shell script and the output of the script will be used
as the module content.
Ref #84
Make sure the previous command has ended before
executing a new command.
This also fixes the execution block that was
caused by the tailing the command output of
action commands.
Fixesjaagr/lemonbuddy#131
