Clean up spacing on Diffusion headers
Summary: This adds some controllable space between paths in Diffusion headers. Fixes T3951
Test Plan: Tested new links in diffusion.
Reviewers: epriestley
Reviewed By: epriestley
CC: Korvin, epriestley, aran
Maniphest Tasks: T3951
Differential Revision: https://secure.phabricator.com/D7304