New implementation of ``MultiFitter``, with more flexible chained fits.
9.5
Adds a new keyword ``linear`` to ``lsqfit.nonlinear_fit(...)`` that lists (optionally) which fit parameters appear linearly in the fit function. These parameters are removed from the fit using *variable projection* and then restored afterwards.
9.4
Minor update: Setting ``p0=True`` causes ``nonlinear_fit()`` to choose the fit search's starting point at random from the prior distribution.
9.3
Adds bootstrap capability to MultiFitter.
9.2
Minor update: new options for ``MultiFitter.make_plot``; updated tests to deal with new ``numpy``.