Check if the output supports colors (fixes #244)

Authored by michalt on May 15 2016, 10:31 AM.

Description

Check if the output supports colors (fixes Trac #244)

This avoids using colors when the output is, e.g., redirected to a
file. This requried a change to avoid passing the --colour flag to
shake (so that hadrian is in charge of colors).

Signed-off-by: Michal Terepeta <michal.terepeta@gmail.com>