google-cloud-storage README example is incorrect

[ifigotin]

We have the following example:
Iterator<Bucket> bucketIterator = storage.list().iterateAll();

However, storage.list().iterateAll() does not return java.util.Iterator, instead
java.lang.Iterable is returned.

Consider changing the example to a 'for' loop, e.g.:

      Storage storage = StorageOptions.getDefaultInstance().getService();
      for(Bucket bucket : storage.list().iterateAll()) {
        ...
      }

[vam-google]

Documentation updated, closing.