Make sure you're using the edu store for your school to take advantage of the best discount. Like most have said, you should really save up the extra $90 and get the RAM (~12 hours of work at $8/hr).
The MBAs and RMBP have a lot of their hardware soldered/glued in so what you buy is what you get. Storage is where it gets a little tricky. That you could replace, but the blade isn't the same as the 2011 MBAs or the RMBP so it might be awhile before aftermarket solutions are available there.
EDIT: 4GB would be fine for your planned activities, but in the event you want to change your major, overall future-proofing, or new hobbies you pick up in college, the 8GB would be better. Adding more RAM to a Mac has always made it feel like a new machine.