test_tiff_file_format: Added for testing the module tiff_file_format. This will address issues #125, #126, #127, and #128.
__init__: Added test_tiff_file_format to __all__ and imported it as well.
tiff_file_format: Updated docstring for convert_tiffs to mention z_index.
test_tiff_file_format: Added test for get_multipage_tiff_shape_dtype from tiff_file_format. This fixes #125.
test_tiff_file_format: Added test for get_multipage_tiff_shape_dtype_transformed from tiff_file_format. This fixes #126.
test_tiff_file_format: Added test for get_multipage_tiff_shape_dtype from tiff_file_format. This fixes #127.