Updates to Steady state module

- Return profile reduction ratio in debug mode when using RCM.
Good idea

> Robert Johansson <mailto:notifications@github.com>
> November 19, 2014 at 11:35
>
> In qutip/steadystate.py:
>
> > @@ -357,7 +361,9 @@ def _steadystate_direct_sparse(L, ss_args):
> > v = spsolve(L, b)
> > _direct_end = time.time()
> > ss_args['info']['solution_time'] = _direct_end-_direct_start
> > -
> > +
> > + ss_args['info']['residual_norm'] = la.norm(b - L*v, np.inf)
>
> How about moving this computation to within the
>
> |if ss_args['return_info']:
> |
>
> statement? Otherwise it will be computed and never used for most 
> cases, since return_info is False by default.
>
> —
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> <https://github.com/qutip/qutip/pull/250/files#r20554809>.
>