R1:4743ad96497b

Miniturize the nav buttons

Summary: This uses the slightly smaller icons. Not sure about the logout icon, will play with it more in the morning.

Test Plan: tested new nav on desktop and mobile.

Reviewers: epriestley

Reviewed By: epriestley

CC: Korvin, epriestley, aran

Differential Revision: https://secure.phabricator.com/D8119