update readme

Author: djih

README.md

@@ -125,13 +125,13 @@ You can pass a callback function to logEvent, which will get called after receiv
 
 The status and response from the server are passed to the callback function, which you might find useful. An example of a callback function which redirects the browser to another site after a response:
 
-'''javascript
+```javascript
   var callback_function = function(status, response) {
     if (status === 200 && response === 'success') {
       // do something here
     }
     window.location.replace('URL_OF_OTHER_SITE');
   };
-'''
+```
 
-In the case that `optOut` is true, then no event will be logged, but the callback will be run. In the case that `batchEvents` is true, if the batch requirements `eventUploadThreshold` and `eventUploadPeriodMillis` are not met when `logEvent` is called, then no request is sent, but the callback is still called.
+In the case that `optOut` is true, then no event will be logged, but the callback will be called. In the case that `batchEvents` is true, if the batch requirements `eventUploadThreshold` and `eventUploadPeriodMillis` are not met when `logEvent` is called, then no request is sent, but the callback is still called. In these cases, the callback will be called with an input status of 0 and response 'No request sent'.