FIXED: Bloch3d vectors always had unit length
FIXED: Bloch3d vectors always had unit length

Rewrote the vector routine for Bloch3d so that the vectors are
nonlonger unit length.  Docstrings need to be rewritten as the
underlying code has greatly changed.

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