Writing 4D images with a single volume

[nilgoyette]

This snippet currently produces a mangled image, as if the bytes are written in the wrong order.

let mut data = Array4::zeros((5, 5, 4, 3));
data.slice_mut(s![.., 2, 2, 0]).fill(1.0);
data.slice_mut(s![.., 3, 2, 0]).fill(1.1);
write_nifti("/tmp/test.nii.gz", &data.select(Axis(3), &[0]), None).unwrap();

Changing the indices to &[0, 1] works well. This tells me that writing a 4D image with a single volume is broken. I had no success fixing it yet but I'm working on it.