add utm params to register api call

Author: thabofletcher

src/js/init-header.js

@@ -1001,6 +1001,12 @@ if (!loginState) {
           } else {
             fields.password = $('#registerForm  input.pwd').val();
           }
+          
+          if (utmSource) {
+            fields.utm_source = utmSource;
+            fields.utm_medium = utmMedium;
+            fields.utm_campaign = utmCampaign;
+          }
 
           if (_kmq) 
             _kmq.push(['identify', fields.email]);