Support ansicon for ANSI support on Windows

Summary: This gives more color. See: https://github.com/adoxa/ansicon

Test Plan: run `arc unit` amongst others and see spiffy colors

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: epriestley, Korvin

Differential Revision: https://secure.phabricator.com/D9560