ReleephRequestStatus

Summary: This is just a bit of gardening in order to make the responsive-UI diff easier; I'll be putting getColorFor($status) type things in this class, following the pattern in ManiphestTaskStatus.

Test Plan: Poke around Releeph.

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, Korvin

Differential Revision: https://secure.phabricator.com/D5893