Finished first version of super_tensor, and unit test works.
Finished first version of super_tensor, and unit test works.

zasdfgbnm/qutip,cgranade/qutip,qutip/qutip,anubhavvardhan/qutip,anubhavvardhan/qutip,zasdfgbnm/qutip,cgranade/qutip,qutip/qutip