Bug in nbodykit.transform.CartesianToSky

[pablocoque]

Describe the bug
When transforming from cartesian to sky coordinates, an error arises regarding the expected and actual dimensions of the output array, e.g. I have a catalog of N objects, the expected array would be Nx3 but output from the function is 3Nx1.
Also, not sure if it is a problem or not, but function won't execute if observer position is just a list, i.e. [x, y, z], it only runs when the input is in daks.array type.

Steps To Reproduce
From any mock catalogue, run the function trying to assign it to new position column in the catalog:

cat['Sky_coords'] = nbodykit.transform.CartesianToSky(pos=cat['Position'], cosmo=cosmo, velocity=None, observer=dask.array.from_array([0, 0, 0]), zmax=100.0, frame='icrs')

Actual behaviour
Returns (if observer position is dask.array type) an array of dimension 3Nx1

Expected behaviour
To obtain an array of dimension Nx3.

Version
version 0.3.16dev0

Additional context
I looked in the source code and found that the problem is when stacking the (RA, DEC, z) arrays into one array, as in the source code:

 return da.stack((ra, dec, z), axis=0)

and should be

 return da.stack((ra, dec, z), axis=1)

or

return da.stack((ra, dec, z), axis=-1)

I implemented this change in my personal installation and worked as expected.