finish implementing N and W tooltips and use W in differential

Summary: 'cuz new fluid layouts require the westerlyness. Looks like D4126 started the N and W implementation but didn't finish it...? note I had to do the shifting of the 5 pixels in javascript; using the CSS didn't work for me in chrome.

Test Plan: uiexample, and hoping it goes well when deployed in prod for differential case

Reviewers: epriestley

Reviewed By: epriestley

CC: chad, aran, Korvin

Maniphest Tasks: T2211

Differential Revision: https://secure.phabricator.com/D4257