Clean up Hovercard CSS

Summary: Cleans up some wonkiness in rendering edge cases, like long titles.

Test Plan:
Test long titles and UI Examples.

{F164546}

{F164547}

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: epriestley, Korvin

Differential Revision: https://secure.phabricator.com/D9433