Come up with a new way to tell if people are on leave

[ErikBoesen]

Currently we just check if the graduation year of each student has increased since the saved copy we have from last year. Once this semester ends, we'll no longer have a reliable way to tell whether people are still on leave or if they only took one semester off. We'll either need to find another way to get leave data, or change the labeling to signify that this student HAS taken a leave but may not necessarily still be on it.