SubscribeBox: React to click on area.

Initially, the subscribe box would only pop up if
you clicked on the envelope.

Now, it pops up if you click in the `subscribeLnk`
id.

This will make it easier for mobile users to
subscribe, as they won't have to be as accurate
when clicking.
Merge pull request #108 from CalPolyIEEE/hotfix-click-subscribe-area-to-subscribe

SubscribeBox: React to click on area.