fixed old code that used dense matrices for some parts of the steady state solver.  This fixes Issue 11 as I have tested it on a 900 x 900 Hamiltonian and it takes about 850 mb per thread.  I could run four threads using slightly over 5Gb of memory.
fixed old code that used dense matrices for some parts of the steady state solver.  This fixes Issue 11 as I have tested it on a 900 x 900 Hamiltonian and it takes about 850 mb per thread.  I could run four threads using slightly over 5Gb of memory.

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