Fix typo on line 360 of event.js

- Had a mistake I caught through manual testing
- Now actually just need to write real test cases

lib/event.js

@@ -357,7 +357,7 @@ var ICalEvent = function(_data, calendar) {
                     throw '`repeating.exclude` contains invalid value `' + excludedDate + '`!';
                 }
 
-                data.repeating.excludedDate.push(excludedDate);
+                data.repeating.exclude.push(excludedDate);
             });
         }