Fix Buzz Integration Failing Tests

* `$url` in `Client::doRequest(...)` uses https protocol
* Fixed calls to `AlgoliaTestCase::safe_name(...)` and `AlgoliaTestCase::containsValue(...)`
* `Client` methods call `Client::request(...)` not `Client::doRequest(...)`
* Marked `FunctionTest::testKeepAlive()` as skipped

Using the http protocol results in an AlgoliaException:
```php
1) AlgoliaSearch\Tests\BasicTest::testAddObject
AlgoliaSearch\AlgoliaException: This method is only available in HTTPS
```