Add the ability to return relative luminance

[mpchadwick]

I need this feature currently for a project I'm working on, pygments-high-contrast-stylesheets.

This script parses the stylesheet and identifies style rules with insufficient color contrast for the text against the background color. It also attempts to provide a recommendation for changing the text color. Whether or not to call lighten or darken depends on the relative luminance of the background and text color. This change would allow me to access that info from this library, which I've been using.

It could come in handy for others as well.

[mkdynamic]

Awesome, thanks!

[mpchadwick]

@mkdynamic Wow. I think this is the fastest I've ever had a PR merged! Excellent job as a maintainer! Would you mind bumping the version and pushing to Ruby gems?

[mkdynamic]

Haha, thanks for making a PR that was an easy merge :)

Just pushed a new version to RubyGems:

$ gem push wcag_color_contrast-0.1.0.gem 
Pushing gem to https://rubygems.org...
Successfully registered gem: wcag_color_contrast (0.1.0)