is h5py dependency required

[ramav87]

We may be able to remove the h5py dependency from sidpy. We should think about how best to go about doing this.

[ssomnath]

Consider moving sidpy.hdf_utils to pyNSID and then having pyUSID import pyNSID. I am not particularly convinced about the benefits of the move. We may want to look into the benefits of removing h5py - is this going to be a major boon to users?

[gduscher]

Made a branch without h5py which tests okay without h5py dependency.
I will try it out for some notebooks soon and report back

[ramav87]

@gduscher are we ready for a PR with removed h5py dependency?