Add grunt task to create archives stamp in header

+ That way users know they are looking at the archives since some of the "newer" archives look eactly the same as the current stuff.
Add archives stamp in header of all pages
Prevent stamp styles from being added twice

+ If the `<style>` tag already exists… do not add it again.
Merge remote-tracking branch 'origin/master' into 0.1.0_0.5.0-wip