added remote-data decorator to BaseImageTests class

I had to add the decorator to the ```BaseImageTests``` class because the images were downloaded in the ```setup_class``` method. Now ```python setup.py test``` skips all the tests in ```test_images.py``` and ```test_transform_coord_meta.py```. Is that a problem?
Can you just write as e.g. 148.5? (just for simplicity)