R1:6d5dcea3ba0f

Inform about disabled and away users in Differential fields

Summary:
I've tried colors, italics, strike-through and this is a compromise between me and @leebyron.

NOTE: I don't want to disturb @epriestley from playing Diablo 3.

Test Plan: {F11439, size=full}

Reviewers: btrahan

Reviewed By: btrahan

CC: aran, epriestley, leebyron

Differential Revision: https://secure.phabricator.com/D2481