systematics docs

[sahiljhawar]

#386

[mcoughlin]

This is excellent. Perhaps do you want to include an example plot from your paper?

[mcoughlin]

I also wonder if we should add your citation to the front README for when folks should cite your paper in particular if they turn on systematics.

[sahiljhawar]

@mcoughlin We haven't use any "systematic corner plots" in the paper, instead we always used the systematics to do interpolation for the light curves which I feel is beyond the scope of the documentation (however I can explain it if someone wants to use it in their workflow).

Citation in front README sounds good to me.