Update Container.php

As is, deleteWithObjects() will fail if container is EMPTY. This is because an object count of zero means $secondsToWait = 0, which means $endTime = time(), which means WHILE loop never runs. Quickest solution was to change "time() < $endTime" to "time() <= $endTime, but it made more sense to just delete the container if it's empty.
make deleteWithObjects() work with empty containers

1) use getObjectCount() to check container size, 2) return early if empty container deleted, 3) conditional syntax changed for PSR-2 compliance, and 4) removed "and all its objects" from container exception message since we can assume objects in container were successfully deleted by deleteAllObjects();
Merge pull request #490 from joshrencher/patch-1

make deleteWithObjects() work with empty containers