antsImage not "arraylike" for numpy operations

[cookpa]

Catches users out like in #862

I think it might be good to provide an explicit error message telling people to use image.numpy() - I will make a PR but as always welcome thoughts from others

[cookpa]

Turns out #862 was another problem entirely, but still, this results in an non-intuitive result without an error

>>> recon_vol = ants.image_read(ants.get_ants_data('mni'))
>>> recon_reg_vol = np.zeros_like(recon_vol, dtype=recon_vol.dtype)
>>> recon_reg_vol
array(0., dtype=float32)