fixing typo

core/js/eventsource.js

@@ -23,7 +23,7 @@
  * wrapper for server side events (http://en.wikipedia.org/wiki/Server-sent_events)
  * includes a fallback for older browsers and IE
  *
- * use server side events with causion, to many open requests can hang the server
+ * use server side events with caution, to many open requests can hang the server
  */
 
 /**