Adds optional label to statistics implementation.

analytics.js

     ga('send', 'pageview');
   }
 
-  Analytics.prototype.sendEvent = function (action, data) {
-    // empty label and add the value, the value should be integer or null
+  Analytics.prototype.sendEvent = function (action, data, label) {
+    // empty label if missing value for it and add the value,
+    // the value should be integer or null
     var value = Math.round(parseFloat(data));
 
-    ga('send', 'event', 'jit.si', action, "", value ? value : null);
+    ga('send', 'event', 'jit.si',
+        action, label ? label : "", value ? value : null);
   };
 
   ctx.Analytics = Analytics;