Respect NO_COLOR environment variable

[tintou]

It seems that there is a consensus on using the NO_COLOR environment variable https://no-color.org/ so we should support that

[leggettc18]

For the Record, NO_COLOR should probably also include removing the dim, bold, and underline control codes as well, would you agree? Or should that be a separate env variable?

[tintou]

It seems that the NO_COLOR is only intended to control the color as per https://github.com/jcs/no_color/issues/220