Final Webhook Management API Changes

- Updated Samples
- Additional Functional Tests
- Enabled Travis to do functional tests (with allowed failures) on each build

sample/notifications/SearchWebhookEvents.php

@@ -12,6 +12,7 @@
 // for a webhook events. This is made in a sample just to make sure there is minimum of one webhook to listen to.
 /** @var \PayPal\Api\Webhook $webhook */
 $webhook = require __DIR__ . '/../bootstrap.php';
+use PayPal\Api\Authorization;
 
 $params = array(
    // 'start_time'=>'2014-12-06T11:00:00Z',
@@ -28,4 +29,5 @@ try {
 
 ResultPrinter::printResult("Search Webhook events", "WebhookEventList", null, $params, $output);
 
+
 return $output;