Update to FontAwesome 4.2.0

Summary: Update the the lastest version, adds payment icons, reduced woff file sizes

Test Plan: load icon examples

Reviewers: btrahan, epriestley

Reviewed By: epriestley

Subscribers: Korvin, epriestley

Maniphest Tasks: T6376

Differential Revision: https://secure.phabricator.com/D10778