Integration test for the Worksheet_Drawing

[liuggio]

After the @mitsurugi https://github.com/liuggio/ExcelBundle/pull/78 , would be great to be consistent and free to upgrate so it would be awesome if you could add an integration test: An example of controller: https://github.com/liuggio/ExcelBundle/blob/master/Tests/app/Controller/FakeController.php#L58 and its integration test: https://github.com/liuggio/ExcelBundle/blob/master/Tests/Controller/FakeControllerTest.php#L40