Disconnect the timer when the element has been removed.

timesince no longer will continue trying to update an element that has
been removed. Previously, it would just yell in the console log every
minute.
Fix the timesince indicator when showing a value less than 1 minute.

When showing a value less than 1 minute, an empty string was being
returned. We were checking if seconds were 0, but we wanted to check
minutes.
Fix an indentation issue.