Subclass of AttachmentCell deleteButton not responding.

[mdescalzo]

Working with the AttachmentManager plugin.

When I implement AttachmentManagerDataSource and use a custom subclass of AttachmentCell (DocumentAttachmentCell) and the provided ImageAttachmentCell class, neither cell responds to taps to the deleteButton. If I disable the AttachmentManagerDataSource and allow the AttachmentManager's default handler generate the cell, the delete button works as expected for ImageCells, but not for the default AttachmentCell.