add function

	add: function (req, res) {
		var id = req.session.Student.id;
		Student.findOne({id: id}).exec(function(err, thisStudent) {
			Course.findOne({unit_code: req.param('unit_code')}).exec(function(err, thisCourse) {
				var creditPoints = thisCourse.credit_points;
				for (i = 0; i < thisStudent.courses.length; i++) {
					creditPoints = creditPoints + parseInt(thisStudent.courses[i].credit_points)
					console.log("in for loop cp is " + creditPoints);
				}

				if (creditPoints > 12) {
					res.redirect('/exceeded_credit_points');
				}

				else {
				console.log("credit points is " + creditPoints);
					thisStudent.courses.add(thisCourse);
					thisStudent.save(function(err, newStudent){});
					res.view({
						course: thisCourse
					});
				}
			});
		});
	},