Suggestion: Update documentation on use of retrieveCloudDocumentWithName

[Seoras]

The documentation section covering retrieveCloudDocumentWithName should be updated with a warning that it is the completion block's responsibility to close the document once opened otherwise deleting it at a later point in time will result in the file auto-magically re-appearing.

I was ready for jumping off a bridge after more than a day wasted on trying to work out why I couldn't delete anything before I stuck the line below in the completion handler right after I'd accessed the file data.

[cloudDocument closeWithCompletionHandler:nil]; 

[neowinston]

Thanks for sharing this important information!