R1:f79975b34092

Update ObjectSelector CSS

Summary: Cleans up the UI a little on the Object Selector.

Test Plan: Test various layouts, attach and unattach tasks and diffs.

Reviewers: epriestley

Reviewed By: epriestley

CC: Korvin, epriestley, aran

Differential Revision: https://secure.phabricator.com/D7661