Respect NO_COLOR env variable

[callmetango]

• disable ANSI color output when NO_COLOR env variable is set

[hartwork]

@callmetango I would submit two pull requests to https://github.com/jcs/no_color for this — one for fetchcommandwrapper and one for aria2c — unless you wanted to do either or both of these. Should I go forward?

[callmetango]

@callmetango I would submit two pull requests to https://github.com/jcs/no_color for this — one for fetchcommandwrapper and one for aria2c — unless you wanted to do either or both of these. Should I go forward?

Er, well, I wasn't even aware that the NO_COLOR list exists. Shure, go for it! ;-)

[hartwork]

@callmetango 2x done:

• Add fetchcommandwrapper jcs/no_color#309
• Add aria2 jcs/no_color#310