fixes #17. better default value for isherm parameter in liouvillian_fast.
fixes #17. better default value for isherm parameter in liouvillian_fast.

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