Restore highlighting when jumping to transactions using URI anchors

Summary:
At some point, the highlighting behavior for the timeline broke. When you follow a link to a particular timeline story, the story should be highlighted.

Prior to this change, the <a /> tag itself highlights, but there's no associated CSS and it's too deep in the tree to do anything useful.

(Since this change is fairly straightforward, I gave up digging for the root cause before finding it.)

Test Plan:

• Clicked a timeline story anchor, saw the story highlight.

Differential Revision: https://secure.phabricator.com/D21213