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