MaxCtrl doesn't strip colors from non-tty output

If the output terminal isn't a TTY, the colors will be printed as-is instead of being displayed as the actual colors. MaxCtrl should check whether the output is a TTY before using colors in the output.

For example, the output of watch maxctrl list servers is malformed due to the fact that it doesn't transform color commands into actual colors by default. A workaround for this is to use watch --color.