"Please Refresh" Notifications

Summary:
Based off D2704. Adds humane.js and a bit of plumbing. Currently does
not seem to load notification.css (which causes notifications not to display)
for reasons entirely opaque to me.

Test Plan:
tried locally. currently works except for the actual display due to
css loading difficulties

Reviewers: epriestley

Reviewed By: epriestley

CC: allenjohnashton, keebuhm, aran, Korvin

Differential Revision: https://secure.phabricator.com/D2705