R1:029fa5b1f31b

Allow `AphrontTagView` subclasses to wrap their tag in a container

Summary: See Conpherence discussion. This probably works?

Test Plan:
Didn't test at all!

bwahaha

Reviewers: chad

Reviewed By: chad

CC: aran

Differential Revision: https://secure.phabricator.com/D6120