Support Display P3 and #rrggbbaa colors

[citrusui]

Safari 10.1 was released in beta today, and will be shipping to macOS 10.12.4 and iOS 10.3 sometime this spring. In summary, a wider array of colors can now be used on the web for Apple devices that support P3 colors.

Since Chromium and EdgeHTML do not yet support these features, I'll need to throw in a few @support queries. It is unknown if Firefox specifically supports Display P3; for now, I will assume it is being considered or in development.

Refs:

• https://developer.apple.com/library/prerelease/content/releasenotes/General/WhatsNewInSafari/Articles/Safari_10_1.html
• http://caniuse.com/#feat=css-rrggbbaa