DUB colored output proposal/showcase

[gdelazzari]

On Friday, 8 June 2018 at 16:11:27 UTC, Basile B. wrote:
> While this look okay please in the initial PR don't forget to 
> add code to deactivate colors when DUB will be piped.

Sure, I won't forget about that. On Linux (and I guess also 
MacOS) it should be enough to check if stdout is a tty (isatty() 
from C std) or not, while I don't know how that could be done on 
Windows. Do you have any idea?