Added custom success, fail, progress event handling

Modified FeedEk to return the promise object so that success/fail/progress events can be chained on. An example calling the basic FeedEk functionality, with success, fail, and progress event functions chained on.
```
$('#divRss').FeedEk({
    FeedUrl : 'http://rss.cnn.com/rss/edition.rss',
  }).then(function(){ /*success*/ }, function(){ /*fail*/ }, function(){ /*progress*/ });
```
See the jQuery Promise object documentation for more options http://api.jquery.com/deferred.promise/