R1:663612fdb442

PHUIBoxView

Summary: Adds a basic div box that takes some styles. Not sure this is the best approach for the spacing, but overall hoping people can spend less time in CSS and just use this class.

Test Plan: UIExamples

Reviewers: epriestley, btrahan

Reviewed By: epriestley

CC: aran, Korvin, AnhNhan

Differential Revision: https://secure.phabricator.com/D5723