- Color: fix colours

Fixes #33 (Colours rendering bug)

CodeRay's internal API we've been relying on has changed. We need to
make some adjustments. Basically, we just wrap colour codes in escape
sequences.

Background:
https://github.com/rubychan/coderay/commit/e2acec3ef141725d2fc264e56d1aa18e838c6acf
Release v1.0.0