check if stdout is a tty

Created by: lilydjwg

I'm using zsh. Once I enjoyed something like this:

mv file `j backup`

And I just pressed Tab to expand the jump to see if it was what I wanted.

But now, I get something like $'\033'\[31m/home/lilydjwg/data/backup$'\033'\[0m instead of a plain path. I think the script should disable color output if stdout is not a tty.