Executes a (shell) command in the background

        :return: the process' pid

def execute_in_background(self):
        """Executes a (shell) command in the background

        :return: the process' pid
        """
        # http://stackoverflow.com/questions/1605520
        args = shlex.split(self.cmd)
        p = Popen(args)
        return p.pid