added a unit tests for neill' new pseudo-inverse spectrum solver
added a unit tests for neill' new pseudo-inverse spectrum solver

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