Executed before the command loop starts.

def preloop(self):
        ''' Executed before the command loop starts. '''
        script_dir = os.path.dirname(os.path.realpath(__file__))
        help_dir = os.path.join(script_dir, HELP_DIR_NAME)
        self.load_forth_commands(help_dir)
        self.load_shell_commands(help_dir)