Change not-reviewed status to gray

Antibody characterization documents with “not reviewed” status were red; they’re now gray.
Merge remote-tracking branch 'origin/master' into 2380-not-reviewed-color
Merge remote-tracking branch 'origin/master' into 2380-not-reviewed-color
Merge pull request #468 from ENCODE-DCC/2380-not-reviewed-color

2380 Change color of not-reviewed documents to gray instead of red