Move Timeline icons to Fonts

Summary: Throwing this up for testing, swapped out all icons in timeline for their font equivelants. Used better icons where I could as well. We should feel free to use more / be fun with the icons when possible since there is no penalty anymore.

Test Plan: I browsed many, not all, timelines in my sandbox and in IE8. Some of these were just swagged, but I'm expecting we'll do more SB testing before landing.

Reviewers: btrahan, epriestley

Reviewed By: epriestley

Subscribers: epriestley, Korvin

Differential Revision: https://secure.phabricator.com/D8827