R1:dc62433d178e

Reduce home nav to 300px.

Summary: Based on loose feedback, reduce the width of the navigation.

Test Plan: Test, reload. Chrome and FF.

Reviewers: epriestley, vrana, btrahan

Reviewed By: epriestley

CC: aran, Korvin

Differential Revision: https://secure.phabricator.com/D4507