Add theExoFop fit as an option to the various plots

[avivajpeyi]

Right now our plots can display the initial fit that we provide to PyMC3 as a staring point for sampling. For example:

priors	posterior	phase

We obtain this initial point by "optimizing" the ExoFOP estimates.

I think it would be useful to allow the user to display the ExoFOP. I have hacked this for the paper (see fig below), but it would be nice to add this in a clean way. We have some infrastructure in place for this already -- the OptimizedParms class. Check out #201 where we also plotted the progress of the optimization.