Fix errors for undefined constants like colors.GREEN in non-ANSI terms
Fix errors for undefined constants like colors.GREEN in non-ANSI terms

Resolves the issue that color constants were conditionally defined but
unconditionally referenced, causing AttributeErrors on any invocation
that falls back to COLORED=False. Defines constants with no-op color
code values so they can still be referenced without cluttering up all
the referencing code with conditionals.

Fixes #112.

google/vroom,malcolmr/vroom