Test for TTY Context before printing progress

[melloc01]

Do you want to request a feature or report a bug?
Improvement

What is the current behavior?
Outputs progress on non-TTY contexts, generating loads of ouput

If the current behavior is a bug, please provide the steps to reproduce.

1. webpack --progress in a non-TTY context

What is the expected behavior?
To not print progress. There's a node api for TTY: https://nodejs.org/api/tty.html

If this is a feature request, what is motivation or use case for changing the behavior?
CI output gets bloated with process output.

[evenstensberg]

Have you tried setting env variables for supports-color? https://github.com/chalk/supports-color/blob/master/test.js#L156-L160

[evenstensberg]

Fixed at #452