Add referrefBy to identify

node_modules/c9/format-user-analytics.js

@@ -20,6 +20,7 @@ define(function(require, exports, module) {
                 lastName: getLastName(user),
                 name: user.fullname || user.name,
                 pricingPlan: user.premium ? "Premium" : "Free",
+                referredBy: user.referrer,
                 region: user.region
             };