Properly ensure timeline items have a 1px spacer

Summary: Some browsers, mobile, didn't show 1px space between objects (due to font renderings). This enforces the size for consistent cross-browser display.

Test Plan: Test IE10

Reviewers: btrahan, epriestley

Reviewed By: epriestley

Subscribers: Korvin, epriestley

Differential Revision: https://secure.phabricator.com/D10970