Fix the great clubfest bug of 2014

Today at clubfest we saw a bunch of people try to enter their email
address and then click submit (to sign up for the digest), only to have
the submit button jump out from under their cursor when the digest
details hid themselves, such that their click missed the button. (This
is why usability testing is important, kids.) Having a small delay
before the details get hidden is one way, though not the most elegant
(because the delay also impacts blur events where the user isn’t trying
to click submit), to make sure the click gets fired on the button.