Add an option for --filter color,pattern pairs

Bump version string to v1.2.

This is the squashed result of Scott's contributions for
https://github.com/goodell/highlight/pull/2
fix recent test additions
cache color translation once for performance
cite Scott's contribution
Merge branch 'pull-req-2'

Scott's contribution plus a few of my related fixes.
Merge branch 'master' of github.com:goodell/highlight

Conflicts:
	highlight
	t/runtests