Stacks with varying image data storage configurations cannot be read#18

`TIF` files may have arbitrary image sizes and storage configurations per frame. `TIFFStack` currently assumes that all images share a common size and storage configuration. This means stacks that do not adhere to this rule cannot be read properly, although a `TIFFStack` object can be successfully created. Frames which have a differing storage configuration to the first frame, will raise an error when data from that frame is requested.